#include<fstream>

using namespace std;

#define input "fts.in"
#define output "fts.out"

ifstream fin (input);
ofstream fout (output);
int main ()
{
    int a,b,c,i,S;
    fin>>a>>b;
    S=0;
    for(i=1;i<=a*b;i++)
    {
                       fin>>c;
                       if(c>0)
                       S+=c;
                       }
                       fout<<S;
                       return 0;
                       }