#include<bits/stdc++.h>
using namespace std;

inline void file(){
	freopen("dvalue.in","r",stdin);
	freopen("dvalue.out","w",stdout);
}
#define inf 0x3f3f3f
#define NUM ch-'0'
inline void read(int &res){
	char ch;
	bool flag=0;
	while(!isdigit(ch=getchar()))
		(flag)&&(ch=='-');
	for(res=NUM ;isdigit(ch=getchar());res=res*10+NUM);
	(flag)&&(res=-res);
}	
int n,m;
const int MAXN = 5001;
struct node{
	int u,v,w;
}e[MAXN];
int cnt=0;
inline void add(int u,int v,int w){
	cnt++;
	e[cnt].u = u;
	e[cnt].v = v;
	e[cnt].w = w;
}
bool app[MAXN];
int fa[MAXN];
bool cmp(const node aa,const node bb){
	return aa.w > bb.w;
}

int find(int i){
	return fa[i]==i?i:fa[i]=find(fa[i]);
}

void union_(int x,int y){
	int xx = find(x);
	int yy = find(y);
	fa[yy] = xx;
}

bool check(){
	int ans=0;
	bool flag=1;
	for(int i=1;i<=n;++i){
		if(fa[i] == i){
			ans++;
			if(ans>1){
				flag = 0;
				break;
			}
		}
		if(!app[i]){
			flag=0;
			break;
		}
	}
	memset(app,0,sizeof app);
	for(int i=1;i<=n;++i){
		fa[i] = i;
	}
	if(flag) return 1;
	else return 0;
}

int main(){
	file();
	read(n);
	read(m);
	for(int i=1;i<=n;++i) fa[i] = i;
	for(int i=1;i<=m;++i){
		int u,v,w;
		read(u);
		read(v);
		read(w);
		add(u,v,w);
	}
	sort(e+1,e+m+1,cmp);
	int ans = inf;
	for(int i=1;i<=m;++i){
		for(int j=i+1;j<=m;++j){
			if(e[i].w - e[j].w >= ans) break;
			else{
				for(int k=i;k<=j;++k){
					union_(e[k].u,e[k].v);
					app[e[k].u] = app[e[k].v] = 1;
				}
				if(check()) ans = e[i].w - e[j].w;
			}
		}
	}
	printf("%d",ans);
	return 0;
}