#include<bits/stdc++.h>

#define gcd(a,b) __gcd(a,b)
#define mod 1000000007
#define INF 0x3f3f3f3f
#define eps 1e-6    
#define pb push_back
#define rep(i,x,y) for(int i=x;i<y;i++)
#define mem(a,x) memset(a,x,sizeof(a))
#define IOS cin.tie(0), ios::sync_with_stdio(false)
#define maxn 1000005
typedef long long ll; 
using namespace std;
int a[3005];
int n,m,u,v,w;
void solve(){
    // scanf("%d%d",&n,&m);
    memset(a,0,sizeof(a));
    int mini=INF;
    rep(i,0,m){
        cin>>u>>v>>w;
        if(u!=v){
            a[u]+=w;
            a[v]+=w;
        }
    }
    sort(a+1,a+n+1);
    rep(i,1,n+1){
        if(a[i]!=0) {mini=a[i]; break;}
    }
    if(mini==INF) mini=0;
    cout<<mini<<endl;
}
int main(){
    // int T=1;
    // cin>>T;
    while(cin>>n>>m){
        solve();
    } 
    return 0;
}