#include<fstream>
using namespace std;
int main()
{
    int n,m,i=1,j=1,s[100][100],suma=0;
    ifstream f("flip.in");
    ofstream g("flip.out");
    f>>n>>m;
    while(!f.eof())
       {
       f>>s[i][j];
       if(s[i][j]>=0)
       suma=suma+s[i][j];
       i++;
       j++;
       };
    g<<suma;
    f.close();
    g.close();
    
    return 0;
}