#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#define MOD 1000000007
#define INF 1e9
#define IN inline
#define RG register
using namespace std;
typedef long long LL;
typedef long double LB;
const int MAXN=5010;
const int MAXM=100010;
inline int max(int &x,int &y) {return x>y?x:y;}
inline int min(int &x,int &y) {return x<y?x:y;}
inline int gi() {
    register int w=0,q=0;register char ch=getchar();
    while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
    if(ch=='-')q=1,ch=getchar();
    while(ch>='0'&&ch<='9')w=w*10+ch-'0',ch=getchar();
    return q?-w:w;
}
struct edge{
    int u,v,w;
    bool operator<(edge a)const{return w<a.w;}
}e[MAXM];
int f[MAXN],ans;
IN int find(int x){return x==f[x]?x:f[x]=find(f[x]);}
void pri(){printf("%d",ans);exit(0);}
int main()
{
    freopen("dvalue.in","r",stdin);
    freopen("dvalue.out","w",stdout);
    int n=gi(),m=gi(),M=0;ans=INF;
    for(int i=1;i<=m;i++)e[i]=(edge){gi(),gi(),gi()};
    sort(e+1,e+1+m);
    for(int i=1;i<=m;i++){
        for(int j=1;j<=n;j++)f[j]=j;
        for(int j=i;j<=m;j++)
            if(find(e[j].u)!=find(e[j].v)){
                M=e[j].w;f[f[e[j].u]]=f[e[j].v];
            }
        find(1);int x=f[1];
        for(int j=2;j<=n;j++){
            find(j);if(f[j]!=x)pri();
        }
        ans=min(ans,M-e[i].w);
    }pri();
    return 0;
}