#include <fstream>

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

int main()
{
    int n, k, i, sum, max, j, nr;

    in>>n>>k;

    max = 0;
    for ( i = 1; i <= k; i++ ){
                sum = 0;
                for ( j = 0; j < i; j++ ) {
                        in>>nr;
                        sum = sum + nr;
                }
                if ( sum > max )
                    max = sum;
    }
    out<<max;



    return 0;
}