#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int a[3001];
const int INF=0x3f3f3f3f; 
int main(){
    int n,m;
    int x,y,z;
    int l,sum;
    while(scanf("%d",&n)!=EOF){
        memset(a,0,sizeof(a));
        scanf("%d",&m);
        for(int i=1;i<=m;i++){
            scanf("%d%d%d",&x,&y,&z);
            if(x!=y){
            a[x]+=z;
            a[y]+=z;}
        }
        l=INF;
        for(int i=1;i<=n;i++){
            l=min(l,a[i]);
        }
        printf("%d\n",l);
    }
    return 0;
}