#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<ll> x(n);
    rep(i, m) {
        int u, v, w;
        cin >> u >> v >> w;
        u--;
        v--;
        x[u] += w;
        x[v] += w;
    }
    sort(x.rbegin(), x.rend());
    ll ans = 0;
    rep(i, n) {
        if (i % 2)
            ans -= x[i];
        else
            ans += x[i];
    }
    cout << ans / 2 << endl;
    return 0;
}