#include<bits/stdc++.h>

using namespace std;


int main()
{
       
       int n,m;
       while(cin >> n >> m){
           long long a[3005] = {0};
           while(m--){
               int num1,num2,num3;
               cin >> num1 >> num2 >> num3;
               if(num1 == num2){
                   continue;
            }
               a[num1] += num3;
               a[num2] += num3;
        }
           long long mi = 10000000000;
           for(int i = 1;i <= n;i++){
               mi = min(mi,a[i]);
        }
           cout << mi << endl;
    }
       
       
       
    return 0;
}