//并查集 测是否连接,更新最小代价
#include <bits/stdc++.h>
#define ll long long 
#define N 3050
#define INF 0x3f3f3f
using namespace std;
int pre[N],h[N],sum[N];

long double aw(long double x1,long double y1,long double x2,long double y2) {
    return sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
}

long double cv(long double a,long double b,long double c) {
    return acos((b*b+c*c-a*a)/(2*b*c));
}

int oneNumInBinary(ll n) { 
    ll cnt=0;
    while(n)  n=n&(n-1),cnt++;
    return cnt;
}

ll qpow(ll a,ll b) {
    ll ans=1;    
    while(b) {       
        if(b&1) ans=(ans*a)%999;        
        a=a*a%999;      
        b>>=1;    
    }   
    return ans;
}

inline int read() {
    int x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

inline string readstring() {
    string str;
    char s=getchar();
    while(s==' '||s=='\n'||s=='\r'){s=getchar();}
    while(s!=' '&&s!='\n'&&s!='\r'){str+=s;s=getchar();}
    return str;
}

int find(int x) {
    int r=x;
    while(r!=pre[r])  r=pre[r];
    return r;
}
 
void Union(int x,int y) {
    int fx=find(x),fy=find(y);
    if(fx!=fy)  pre[fy]=fx;
}

int main()
{
    int n,m,a,b,w;
    while(~scanf("%d %d",&n,&m)&&n!=0)
    {
        int ans=0;
        for(int i=0; i<n; i++)  pre[i]=i;
        memset(sum,0,sizeof(sum));
        for(int i=1; i<=m; i++)
        {
            scanf("%d %d %d",&a,&b,&w);
            if(a==b)  continue;
            sum[a] += w;
            sum[b] += w;
            int t1 = find(a);
            int t2 = find(b);
            if(t1!=t2)  {
                pre[t1]=t2;
                ans++;
            }
        }
        if(ans==n-1)  {
            sort(sum+1,sum+1+n);
            cout<<sum[1]<<endl;
        }
        else    cout<<0<<endl;
    }
    return 0;
}