#include<cstdio>
#include<cstring>
#include<vector>
#include<stack>
#include<cctype>
#include<cmath>
#include<algorithm>
#include<iostream>
#include<queue>
#include<time.h>
#define ll long long
using namespace std;
/*maaaarrrrrx*/
//排序之后相减就最小 
int maxd=99999,mind=-99999;
short isc[5002]={0};
int n,m,np=0;
int first[5002],last[5002];
struct edge{
	int u,v,t;
	friend bool operator <(edge a,edge b){return a.t<b.t;}
}e[5002];
int fa[5002],ans=9999999;
int flag;
int find(int x)
{return x==fa[x]? x:fa[x]=find(fa[x]);}//yasuolujing 
void solve()
{
	for(int i=1;i<=m;i++)
	{
		for(int j=1;j<=n;j++)fa[j]=j;//memset fa[];
		for(int j=i;j<=m;j++)
			if(find(e[j].u)!=find(e[j].v))
			{flag=e[j].t;fa[fa[e[j].u]]=fa[e[j].v];}
		find(1);int x=fa[1];
        for(int j=2;j<=n;j++)
		{
			find(j);
			if(fa[j]!=x)//接下：如果没有连通就退出
			{cout<<ans<<endl;exit(0);}
		}
		ans=min(ans,flag-e[i].t);	
	}
	cout<<ans<<endl;
}
int main()
{
//	freopen("i.txt","r",stdin);
	freopen("dvalue.in","r",stdin);
	freopen("dvalue.out","w",stdout);
	scanf("%d%d",&n,&m);
	int x,y,t;
	for(int i=1;i<=m;i++)
	{scanf("%d%d%d",&x,&y,&t);e[i]=(edge){x,y,t};}
	sort(e+1,e+1+m);
	solve();
	return 0;
}