//minamoto

 #include<cstdio>

 #include<algorithm>

 #include<iostream>

 #define inf 0x3f3f3f3f

 using namespace std;

 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)

 char buf[<<],*p1=buf,*p2=buf;

 template<class T>inline bool cmin(T&a,const T&b){return a>b?a=b,:;}

 inline int read(){

     #define num ch-'0'

     char ch;bool flag=;int res;

     while(!isdigit(ch=getc()))

     (ch=='-')&&(flag=true);

     for(res=num;isdigit(ch=getc());res=res*+num);

     (flag)&&(res=-res);

     #undef num

     return res;

 }

 const int N=,M=,K=N+M;

 struct edge{

     int u,v,e;

     inline bool operator <(const edge &b)const

     {return e<b.e;}

 }e[M];

 int fa[K],ch[K][],s[K],mn[K],rev[K],top,v[K],vis[M],f[N];

 int ff(int x){return f[x]==x?x:f[x]=ff(f[x]);}

 inline bool isroot(int x){return ch[fa[x]][]!=x&&ch[fa[x]][]!=x;}

 inline int get(int x,int y){return v[x]<v[y]?x:y;}

 inline void pushup(int x){mn[x]=get(x,get(mn[ch[x][]],mn[ch[x][]]));}

 inline void pushdown(int x){

     if(x&&rev[x]){

         swap(ch[x][],ch[x][]);

         rev[ch[x][]]^=,rev[ch[x][]]^=;

         rev[x]=;

     }

 }

 void rotate(int x){

     int y=fa[x],z=fa[y],d=ch[y][]==x;

     if(!isroot(y)) ch[z][ch[z][]==y]=x;

     fa[x]=z,fa[y]=x,fa[ch[x][d^]]=y,ch[y][d]=ch[x][d^],ch[x][d^]=y,pushup(y);

 }

 void splay(int x){

     s[top=]=x;for(int i=x;!isroot(i);i=fa[i]) s[++top]=fa[i];

     while(top) pushdown(s[top--]);

     for(int y=fa[x],z=fa[y];!isroot(x);y=fa[x],z=fa[y]){

         if(!isroot(y))

         ((ch[y][]==x)^(ch[z][]==y))?rotate(x):rotate(y);

         rotate(x);

     }

     pushup(x);

 }

 void access(int x){

     for(int y=;x;x=fa[y=x])

     splay(x),ch[x][]=y,pushup(x);

 }

 inline void makeroot(int x){

     access(x),splay(x),rev[x]^=;

 }

 inline void link(int x){

     makeroot(e[x].u);

     fa[fa[e[x].u]=N+x]=e[x].v;

 }

 inline void cut(int x){

     access(e[x-N].u),splay(x);

     ch[x][]=ch[x][]=fa[ch[x][]]=fa[ch[x][]]=;

     /*因为link的时候把u的父亲设为边，所以u的深度最低

     把它到根节点的路径打通就好了*/

 }

 int main(){

     //freopen("testdata.in","r",stdin);

     int n=read(),m=read();

     int ans=;

     for(int i=;i<=n;++i) f[i]=i,v[i]=inf;

     for(int i=;i<=m;++i){

         int u=read(),v=read(),k=read();

         e[i]=(edge){u,v,k};

     }

     sort(e+,e++m);

     for(int cnt=,h=,i=;i<=m;++i){

         v[i+N]=e[i].e;

         int u,v;

         if(ff(u=e[i].u)!=ff(v=e[i].v)){

             vis[i]=,link(i),f[f[u]]=f[v],++cnt;

             if(cnt==n) ans=e[i].e-e[h].e;

         }

         else{

             if(u==v) continue;

             vis[i]=;

             makeroot(u),access(v),splay(v);

             vis[mn[v]-N]=;while(!vis[h]) ++h;

             cut(mn[v]),link(i);

             if(cnt==n) cmin(ans,e[i].e-e[h].e);

         }

     }

     printf("%d\n",ans);

     return ;

 }