#include<iostream>
#include<cstdio>
#include<algorithm>
#define sc(x) scanf("%d",&x)
using namespace std;

int main(void) {
    int n, m;
    while (cin>>n>>m) {
        int sum[3010]; for (int i = 1; i <= n; i++)sum[i] = 0;

        for (int i = 0; i < m; i++) {
            int u, v, w; sc(u); sc(v); sc(w);
            if (u == v)continue;
            sum[u] += w;
            sum[v] += w;
        }
        sort(sum + 1, sum + 1 + n);
        printf("%d\n", sum[1]);
        }
    
    return 0;
}