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

int main()
{	
	unsigned int n,m;
	ifstream f("flip.in");
	ofstream g("flip.out");
	 int a[1000][1000],s=0,nr=0;
	f>>n; f>>m;
	 for(int j=1;j<=m;j++)
	  for(int i=1;i<=n;i++)
	  	{ f>>a[i][j];
	      if(a[i][j]>=0)
		    s=s+a[i][j];
	    }
    
	g<<s<<endl;
	
	f.close();
	g.close();
	return 0;
}