#include <algorithm>

#include <iostream>

#include <cstdio>

using namespace std;

int n,m,tot,day,tot_fa,ans;

int fa[];

bool num[];

struct node

{

    int x,y,t;

} w[];

bool cmp(node a,node b)

{

    return a.t<b.t;

}

int find(int x)

{

    if(x!=fa[x])

        return fa[x]=find(fa[x]);

    return x;

}

int main()

{

    cin>>n>>m;

    for(int i=;i<=n;i++)    fa[i]=i;

    for(int i=;i<=m;i++)

        cin>>w[i].x>>w[i].y>>w[i].t;

    sort(w+,w+m+,cmp);

    for(int i=;i<=m;i++)

    {

        int fa_x=find(w[i].x),fa_y=find(w[i].y);

        if(fa_x!=fa_y)

        {

            fa[fa_x]=fa_y;

            day=max(day,w[i].t);

            ans++;

        }

        if(ans==n-)

        {

            cout<<day;

            return ;

        }

    }

    cout<<-;

    return ;

}