#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
#include<cstring>
using namespace std;
typedef long long ll;

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

void print(ll x)
{
    if(x<0){putchar('-');x=-x;}
    if(x>9)print(x/10);
    putchar(x%10+'0');
}

ll n,m;
struct node{ll u,v,dis;}E[1000010];
ll fa[1000010];
ll maxn,minn;
ll ans=1e9;
bool cmp(node a,node b){return a.dis<b.dis;}

ll find(ll x)
{
	ll a=x;
	while(x!=fa[x])
	x=fa[x];
	
	while(a!=fa[a])
	{
		int temp=a;
		a=fa[a];
		fa[temp]=x;
	}
	return x;
}

void kruskal(int k)
{
    ll num=0;
    for(int i=1;i<=n;i++)
    fa[i]=i;
    
    for(int i=k;i<=m;i++)
    {
        int fu=find(E[i].u);
        int fv=find(E[i].v);
        if(fu!=fv)
        {
            fa[fu]=fv;
            num++;
            if(num==1) minn=E[i].dis;
            if(num==n-1)
            {
            	if(E[i].dis-minn<ans)ans=E[i].dis-minn;
            	break;
			}
        }
    }
}

int main()
{
	freopen("dvalue.in","r",stdin);
	freopen("dvalue.out","w",stdout);
	
	n=read();m=read();
	for(ll i=1;i<=m;i++)
	E[i].u=read(),E[i].v=read(),E[i].dis=read();
	sort(E+1,E+m+1,cmp);
	
	for(int i=1;i<=m-n+1;i++)
	kruskal(i);
	
	print(ans);
	
	fclose(stdin);
	fclose(stdout);
	
	return 0;
}