#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int main()
{
    long int a[1000][1000], s=0, i, j, N,M;
    fin >> N >> M;
    for( i = 0; i < N; i++)
        for( j = 0; j < M; j++)
            {
                fin >> a[i][j];
                if(a[i][j] > 0)
                    s = s + a[i][j];

            }
    fout << s;
    fin.close();
    fout.close();
    return 0;
}