#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int main()
{
    int n, m, x;
    long long s=0;
    fin >> n >> m;
    int l=m;
    while(n)
    {
        while(m)
        {
            fin >> x;
            if(x>0)
                s+=x;
            m--;
        }
        n--;
        m=l;
    }
    fout << s;
    return 0;
}