#include<bits/stdc++.h>
using namespace std;
struct data
{
    int x,y,z;
}a[15001];
int n,m1,l,r,ans=100000000;
int f[2001];
inline bool cmp(data a,data b)
{return a.z<b.z;}
inline int get(int x){return (f[x]==x)?x:f[x]=get(f[x]);}
int main()
{
	freopen("dvalue.in" ,"r", stdin);
    freopen("dvalue.out","w",stdout);
    cin>>n>>m1;
    for(int i=1;i<=m1;i++) 
	cin>>a[i].x>>a[i].y>>a[i].z;
    sort(a+1,a+1+m1,cmp);
    while(true)
    {
        for(int i=1;i<=n;i++) f[i]=i;
        int k=0;
        l++;
        while(++r<=m1)
        {
            int f1=get(a[r].x),f2=get(a[r].y);
            if(f1!=f2)
            {
                f[f1]=f2;
                if(++k==n-1)
                {
                    if(a[r].z-a[l].z<ans) 
					ans=a[r].z-a[l].z;
                    break;
                }
            }
        }
        if(k<n-1) break;
        for(int i=1;i<=n;i++) 
		f[i]=i;
        k=0;
        l=r+1;
        while(--l>=1)
        {
            int f1=get(a[l].x),f2=get(a[l].y);
            if(f1!=f2)
            {
                f[f1]=f2;
                if(++k==n-1)
                {
                    if(a[r].z-a[l].z<ans) 
					ans=a[r].z-a[l].z;
                    break;
                }
            }
        }
        if(k<n-1) 
		break;
        r=l;
    }
    printf("%d",ans);
    return 0;
}