#include <bits/stdc++.h>
using namespace std;
int main() {
  int m, n;
  cin >> m;
  int a[m];
  for (int i = 0; i < m; i++) {
    a[i] = 0;
  }
  cin >> n;
  int p = 0, q = 0, r = 0;
  for (int i = 0; i < n; i++) {
    cin >> p;
    cin >> q;
    cin >> r;
    a[p - 1] -= r;
    a[q - 1] += r;
  }
  int res = 0;
  for (int i = 0; i < m; i++) {
    if (a[i] > 0) res += a[i];
  }
  cout << res;
  return 0;
}
