#include <fstream>

using namespace std;
ifstream fin ("transport.in");
ofstream fout ("transport.out");

int n, k, i, j, p, maxim, volum, nrcam, v[16001];
int main()
{
    fin >> n >> k;
    for(i=1; i<=n; i++){
        fin >> v[i];
    }
    j = 1;
    while (nrcam <= k){
        volum = 0;
        for (i=j; i<=nrcam+j-1; i++){
            volum+=v[i];
        }
        j = nrcam + j;
        if (volum >= maxim){
            maxim = volum;
        }
        nrcam++;
    }
    fout << maxim;
    return 0;
}