#include <fstream>
using namespace std;
ifstream cin("transport.in");
ofstream cout("transport.out");

long long A[100013],suma,i,n,aux(0),maxim(-1<<18),k;

int main()
{
 cin>>n>>k;
 for (i=1;i<=n;++i) cin>>A[i], suma+=A[i];
 suma/=k; i=0;
 while(i<n){
            ++i;
            aux+=A[i];
            if (aux>suma) maxim=max(maxim,aux), aux=0;
            }
 cout<<maxim<<"\n";
return 0;
}