#include <iostream>
#include <algorithm>
#include <cstdio>
#include <string.h>

using namespace std;

int main() {
    int m, n;
    int sum[10000];
    while (~scanf("%d%d", &n, &m)) {
        memset(sum, 0, sizeof(sum));
        for (int i = 1; i <= m; i++) {
            int a, b, c;
            cin >> a >> b >> c;
            if (a == b)
                continue;
            sum[a] += c, sum[b] += c;
        }
        sort(sum + 1, sum + n + 1);
        cout << sum[1] << endl;
    }
    return 0;
}