#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int a,b,i=0,ii,S=0,x;
    fin>>a>>b;
    while(i<a){
        ii=0;
        while(ii<b){
            fin>>x;
            if(x>0){
                S=S+x;
            }
            ii++;
        }
        i++;
    }
    fout<<S;
    return 0;
}