#include <fstream>
using namespace std;
ifstream in("flip.in");
ofstream out("flip.out");
int main()
{
    int n,m,s=0,x;
    in>>n>>m;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
    {
        cin>>x;
        if(x>0)
            s=s+x;
    }
    out<<s;
    return 0;
}