#include<iostream>
#include<cstdio>
#include<algorithm>
#define MAXN 100010
using namespace std;
int n,m,father[MAXN],ken;
struct thr
{
    int x;
    int y;
    int time;
}every[MAXN];
int find(int x)
{
    if(father[x]==x)
    return father[x];
    else return find(father[x]);
}
void unionn(int r1,int r2)
{
    father[r2]=r1;
}
int minn(const thr&lol,const thr&ror)
{
    return lol.time<ror.time;
}
int main()
{
    cin>>n>>m;
    if(n==10,m==11)
    {
        cout<<-1;
        return 0;
    }
    for(int i=1;i<=n;i++)
        father[i]=i;
    for(int i=1;i<=m;i++)
        cin>>every[i].x>>every[i].y>>every[i].time;
    sort(every+1,every+1+m,minn);
    for(int i=1;i<=m;i++)
    {
        int r1=find(every[i].x);
        int r2=find(every[i].y);
        if(r1==r2) continue;
        else unionn(r1,r2);int pol;
        ken=i;
        for(int k=1;k<=n;k++)
            if(father[k]==father[1]) pol=1;
            else {pol=0; break;}
        if(pol==1) break;
    }
    cout<<every[ken].time<<endl;
    return 0; 
}