#include<iostream>
#include<fstream>
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
using namespace std;
int m,n,s,v;
int main()
{
    ifstream f("flip.in"); ofstream g("flip.out");
    f>>n; f>>m;
    while(f>>v)
      if(v>-1) s+=v;
    g<<s;
    f.close();
    g.close();
    return 0;
}