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#include <iostream>
#include <cstdint>
#include <vector>
#include <utility>
#include <algorithm>
#include <bitset>
#include <limits>

using namespace std;

int bitcount(int64_t n){
    return std::bitset<64>(n).count();
}

/*int bitcount(
 * int64_t n){
    int acc=0;
    while (n>0){
        acc += (n&1);
        n/=2;
    }
    return acc;
}*/

void  go(){
    int n;
    int64_t m;

    cin>>n>>m;

    if (m==0){
        cout<<0<<endl;
        return;
    }

    vector<int64_t> a(n,0);

    for (auto& x : a)
        cin>>x;

    vector<pair< int64_t,int64_t> > J, J2;

    int sekunda =0;
    if (a[0]>=0)
        J.push_back( make_pair(-1,0));// pioseka konczaca sie z bitem b i na łaczną warttość v
    else{
        sekunda=1;
        J.push_back( make_pair(0,0));
    }


    for (; sekunda < n; sekunda++){
        for (const auto & eJ: J ){
            int64_t b = eJ.first+1;
            int64_t val = eJ.second;
            int64_t inc = 1;
            if (a[sekunda]>=0){
                int bitc = bitcount(b);
                while (b<=m){
                    J2.push_back( make_pair(b, val + a[sekunda]*bitc ) );
                    while ((b & inc) >0) inc*=2;
                    b+=inc;
                    bitc++;
                }
            }else{
                while (b<=m){
                    int bitc = bitcount(b);
                    J2.push_back( make_pair(b, val + a[sekunda]*bitc ) );
                    do{
                        while ((b & inc) == 0) inc*=2;
                        b+=inc;
                    }while ( (b & (2*inc)) == 1 );
                    bitc++;


                }

            }
        }

        sort(begin(J2),end(J2),
             [](const pair< int64_t,int64_t>& a, const pair< int64_t,int64_t>& b ){
                //return a.first<b.first || (!(a.first<b.first) && a.second>b.second);
                return a.first<b.first || ((a.first==b.first) && a.second>b.second);
              }
                        );
        J.clear();

        int64_t max_val=numeric_limits<int64_t>::min();
        for (auto eJ : J2){
            if (eJ.second > max_val){
                max_val = eJ.second;
                J.push_back(eJ);
            }
        }
       // cout<<sekunda<<" "<<J.size()<<" "<<J2.size()<<endl;
        J2.clear();
    }

    cout<<J.back().second<<endl;
}


int main(){
    std::ios::sync_with_stdio(false);
    go();
    return 0;
}