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#include <algorithm>
#include <iostream>
#include <vector>
#include <bitset>
#include <climits>
#include <set>
#include <cassert>

using namespace std;
#define ll long long
#define ull unsigned ll
#define int2 pair<int, int>
#define ll2 pair<ll, ll>
#define ull2 pair<ull, ull>
#define mp make_pair
#define x first
#define y second
#define forEach(a) for(int i = 0; i < a.size(); i++)

const int size = 1e5 + 9;

vector<ll> tab;

int N;
ll M;
int mlog;

ll changeValue(ll v, int pos, bool one, bool increasing) {
    // if (pos == 0) {
    //     if (increasing)
    //         return v | 1;
    //     return v - (v % 2);
    // }

    v >>= pos;
    if (increasing)
        v |= (ll)1;
    else
        v -= (v % 2);
    v <<= pos;

    if (one)
        v -= 1;

    if (increasing)
        v |= (ll)1 << pos;

    return v;
}

//__builtin_popcountll
void nextSet(set<ll2> &values, set<ll2> &out, ll a, int ind, bool increasing) {// x = sum, y = val at b[i]
    // set<ll2> out;
    // cout << "Values size: " << values.size() << " " << a << "\n";
    bool positive = a > 0;
    set<ll2>::iterator it = values.begin();

    while (it != values.end()) {
        ll2 p = *it;
        ll val = p.y;

        for (int i = mlog; i >= 0; i--) {
            ll flag = (ll)1 << i;

            if (flag > M)
                continue;

            // cout << i << "Nex value: " << flag << "\n";

            ll newVal;
            if ((val & flag) > 0 && !increasing)
                newVal = changeValue(val, i, positive, increasing);
            else if ((val & flag) == 0 && increasing)
                newVal = changeValue(val, i, positive, increasing);
            else
                continue;


            if (newVal <= M) {

                // bool addIt = newVal <= M;
                ll bits = __builtin_popcountll(newVal);
                //cout << "Bits " << bits << "\n";
                ll newSum = p.x + a * bits;

                //cout << i <<  " New sum: " << newSum << "\n";

                // if (!addIt && increasing)
                //     break;

                set<ll2>::iterator it2 = out.upper_bound(mp(newSum, LLONG_MIN));
                if (it2 != out.end()) {
                    ll val2 = (*it2).y;
                    //cout << "Val2: " << val2 << "\n";
                    if (newVal >= val2 && increasing) {
                        // if (positive != increasing)
                        //     continue;
                        break;//addIt = false;
                        //cout << "Breaking: " << newSum << ", " << newVal << " a: " << a << " " << val2  << " " << p.x << "\n";
                        // continue;
                    }
                    else if (newVal <= val2 && !increasing) {
                        // if (positive != increasing)
                            // continue;
                        break;
                    }
                }

                // if (addIt) {
                    //cout << "Adding: " << newSum << ", " << newVal << " a: " << a << "\n";
                    out.insert(mp(newSum, newVal));
                // }
                // else
                    //cout << "Not Adding: " << newSum << ", " << newVal << "\n";
            }

        }

        if (ind == N - 1) {
            ll newVal = M;
            ll bits = __builtin_popcountll(newVal);
            ll newSum = p.x + a * bits;

            bool ok = true;
            set<ll2>::iterator it2 = out.upper_bound(mp(newSum, LLONG_MIN));
            if (it2 != out.end()) {
                ll val2 = (*it2).y;
                if (newVal >= val2 && increasing)
                    ok = false;
                else if (newVal <= val2 && !increasing)
                    ok = false;
            }

            if (ok)
                out.insert(mp(newSum, newVal));
        }

        it++;
    }
}

ll maxFromSet(set<ll2> &values) {


    set<ll2>::iterator it = values.begin();
    ll out = LLONG_MIN;

    while (it != values.end()) {
        out = max(out, (*it).x);
        // cout << "Out: " << out << "\n";

        it++;
    }

    return out;
}

void makeSet(int start, int end, set<ll2> &out, bool rev) {
    set<ll2> current[2];
    if (!rev)
        current[start % 2].insert(mp((ll)0, (ll)0));
    else
        current[(end - 1) % 2].insert(mp((ll)0, (ll)M + 1));

    if (rev) {
        for(int i = end - 1; i >= start; i--) {
            // cout << "N: " << i << "\n";
            current[(i + 1) % 2].clear();
            if (tab[i] == 0) {
                swap(current[0], current[1]);
            }
            else
                nextSet(current[i % 2], current[(i + 1) % 2], tab[i], i, !rev);
        }
        swap(current[(start + 1) % 2], out);
    }
    else {
        for(int i = start; i < end; i++) {
            // cout << "N: " << i << "\n";
            current[(i + 1) % 2].clear();
            if (tab[i] == 0) {
                swap(current[0], current[1]);
            }
            else
                nextSet(current[i % 2], current[(i + 1) % 2], tab[i], i, !rev);
        }
        swap(current[end % 2], out);
    }
}

ll iterateMax(set<ll2> &av, set<ll2> &bv) {
    ll out = LLONG_MIN;

    if (bv.size() == 0)
        return out;

    set<ll2>::iterator it = av.begin();
    while (it != av.end()) {
        ll2 val = *it;
        set<ll2>::iterator it2 = bv.end();
        it2--;

        while (it2 != bv.end()) {
            ll2 val2 = *it2;

            if (val.y < val2.y) {//dol , w gore
                out = max(out, val.x + val2.x);
                // cout << "Vals: " << val.x << " + " << val2.x << "\n";
                break;
            }

            if (it2 == bv.begin())
                break;
            it2--;
        }

        // if (it2 == bv.begin())
        //     break;
        it++;
    }

    return out;
}

ll mim() {
    int MID = min((N + 1) / 2, N);

    set<ll2> sets[3];
    makeSet(0, MID, sets[0], false);
    makeSet(1, MID, sets[1], false);
    makeSet(MID, N, sets[2], true);

    return max(iterateMax(sets[0], sets[2]), iterateMax(sets[1], sets[2]));
}

ll obtainMax(int start) {
    set<ll2> current[2];
    current[start % 2].insert(mp((ll)0, (ll)0));

    for(int i = start; i < N; i++) {
        // cout << "N: " << i << "\n";
        current[(i + 1) % 2].clear();
        if (tab[i] == 0) {
            swap(current[0], current[1]);
        }
        else
            nextSet(current[i % 2], current[(i + 1) % 2], tab[i], i, true);
    }

    // cout << current[N % 2].size() << "\n";

    return maxFromSet(current[N % 2]);
}

void init() {
    cin >> N >> M;
    tab.resize(N);

    for(int i = 0; i < N; i++)
        cin >> tab[i];
}

void solve() {
    mlog = 0;
    for (int i = 62; i >= 0; i--)
        if (((1 << i) & M) > 0) {
            mlog = i;
            break;
        }

    if (N <= 151)
        cout << max(obtainMax(0), obtainMax(1)) << "\n";
    else
        cout << mim() << "\n";
}


int main(int argc, const char * argv[]) {

    // ios_base::sync_with_stdio(false);
    // cin.tie(NULL);
    // cout.tie(NULL);

    // cout << changeValue(10, 2, false, true) << "\n";
    // assert(changeValue(10, 2, false, true) == 12);


    init();
    solve();


    return 0;
}

/*
100 1000000000000000
1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1  1 -1 1 -1 1 -1 1 -1 1 -1

ODP: 2203
*/