/* -*- coding: utf-8 -*-
 *
 * 3751.cc:  No.3751 Nonopoly - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

using ll = long long;

/* global variables */

ll ds[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 0; i < m; i++) {
    int u, v, w;
    scanf("%d%d%d", &u, &v, &w);
    u--, v--;
    ds[u] += w, ds[v] += w;
  }

  sort(ds, ds + n);

  ll sum = 0;
  for (int i = n - 1, sgn = 1; i >= 0; i--, sgn *= -1)
    sum += ds[i] * sgn;

  printf("%lld\n", sum / 2);
  
  return 0;
}