#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N, M;
    cin >> N >> M;

    vector<long long> degree(N, 0);

    for (int i = 0; i < M; ++i) {
        int u, v;
        long long w;
        cin >> u >> v >> w;

        --u;
        --v;

        degree[u] += w;
        degree[v] += w;
    }

    sort(degree.begin(), degree.end(), greater<long long>());

    long long twiceScore = 0;

    for (int i = 0; i < N; ++i) {
        if (i % 2 == 0) {
            twiceScore += degree[i];
        } else {
            twiceScore -= degree[i];
        }
    }

    cout << twiceScore / 2 << '\n';

    return 0;
}