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#include<bits/stdc++.h>
using namespace std;


const int N = 205;


int n;
long long m, a[N];

inline long long get(long long val, int bits){
    if(val == -1){
        return (1LL << bits) - 1;
    }
    long long res = 9e18, cur = 0;
    for(int i = 59; i >= 0; i--){
        if((val >> i) & 1){
            bits -= 1;
            if(bits < 0){
                break;
            }
            cur ^= (1LL << i);
        }
        else if(bits > 0 && i >= bits - 1){
            res = min(res, (cur ^ (1LL << i) ^ ((1LL << (bits - 1)) - 1)));
        }
    }
    return res;
}
long long rec(int pos = 1, long long prv = -1, bool firstt = true){
    if(pos == n + 1){
        return 0;
    }
    long long ans = -9e18;
    if(a[pos] <= 0){
        for(int i = 0; i < 60; i++){
            long long x = get(prv, i);
            if(prv < x && x <= m){
                ///cout << "KEK JEDEN: " << pos << " " << i << " " << prv << " " << x << " " << rec(pos + 1, x) << " " << a[pos] * i << "\n";
                ans = max(ans, rec(pos + 1, x, false) + a[pos] * i);
            }
        }
    }
    else{
        for(int i = 59; i >= 0; i--){
            long long x = get(prv, i);
            if(prv < x && x <= m){
                ///cout << "KEK DWA: " << pos << " " << i << " " << prv << " " << x << " " << rec(pos + 1, x) << " " << a[pos] * i << "\n";
                ans = max(ans, rec(pos + 1, x, false) + a[pos] * i);
            }
        }
    }
    return ans;
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> m;
    for(int i = 1; i <= n; i++){
        cin >> a[i];
    }
    cout << rec(1);
}