#include <iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define Nmax 250001
#define inf 100005
using namespace std;
#define DIM 10000
priority_queue<pair <int,int> ,vector<pair<int,int> >, greater<pair <int,int> > >h;
char buff[DIM];
int poz=0;

void citeste(int &numar)
{
     numar = 0;
     //cat timp caracterul din buffer nu e cifra ignor
     while (buff[poz] < '0' || buff[poz] > '9')
          //daca am "golit" bufferul atunci il umplu
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     //cat timp dau de o cifra recalculez numarul
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     }
}
int n,m,x,y,i,j,cost[Nmax],cst,sol,ans,s[Nmax];
vector<pair<int,int> >v[Nmax];
void Dijkstra(int p)
{
    int k;
    cost[p]=0;
    h.push(make_pair(0,p));
    while(h.size())
    {
        int nod=h.top().second;
        int cst=h.top().first;
        sol=max(sol,h.top().first);
        s[nod]=min(s[nod],sol);
        ans=max(ans,s[nod]);
        h.pop();
        for(k=0;k<v[nod].size();k++)
        {
            if(cost[v[nod][k].second] > v[nod][k].first)
            {
                cost[v[nod][k].second]=v[nod][k].first;
                h.push(make_pair(max(sol,v[nod][k].first),v[nod][k].second));
            }
        }
    }


    /*int i,k;
    for(i=1;i<=n;i++)
    {
        heap_node[i]=i;
        h[i].cost=inf;
        h[i].nod=i;
    }
    h[p].cost=0;
    BuildHeap();
    bool ok=1,ok1=1;
    while(n>1 && ok)
    {
        j=extractMin();
        if(j==y)
            ok=0;
        sol=max(sol,h[heap_node[j]].cost);
        int sz=v[j].size();
        for(k=0;k<sz&&ok;k++)
        {
            jh=heap_node[v[j][k].first];
            if(v[j][k].second<h[jh].cost)
            {
                h[jh].cost=max(sol,v[j][k].second);
                up(jh);
            }
        }
        cut(heap_node[j]);
    }*/
}
int main()
{
    freopen("pscnv.in","r",stdin);
    freopen("pscnv.out","w",stdout);
    citeste(n);
    citeste(m);
    citeste(x);
    citeste(y);
    for(;m;m--)
    {
        citeste(i);
        citeste(j);
        citeste(cst);
        v[i].push_back(make_pair(cst,j));
    }
    for(i=1;i<=n;i++)
        cost[i]=s[i]=inf;
    Dijkstra(x);
    cout<<ans;
}