#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int n, m;
  cin >> n >> m;
  vector<long long> w(n);
  for (int i = 0; i < m; ++i)
  {
    int a, b, c;
    cin >> a >> b >> c;
    --a, --b;
    w[a] += c;
    w[b] += c;
  }
  sort(w.rbegin(), w.rend());
  long long ans = 0;
  for (int i = 0; i < n; ++i) ans += (i % 2 ? -w[i] : w[i]);
  cout << ans / 2 << endl;
}