#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,m,x,y,z,a[3009]; 
inline ll read(){
    ll s = 0,w = 1;
    char ch = getchar();
    while (ch > '9' || ch < '0'){ if (ch == '-') w = -1; ch = getchar();}
    while (ch <= '9' && ch >= '0') s = (s << 1) + (s << 3) + (ch ^ 48),ch = getchar();
    return s * w;
}
int main(){
    while (cin>>n){
        m = read();
        fill(a + 1,a + n + 1,0);
        for (ll i = 1;i <= m;i += 1){
            x = read(),y = read(),z = read();
            if (x == y) continue;
            a[x] += z,a[y] += z;
        }
        sort(a + 1,a + n + 1);
        printf("%lld\n",a[1]);
    }
    return 0;
}