#include<bits/stdc++.h>
using namespace std;
ifstream f("pscnv.in");
ofstream g("pscnv.out");
int n,m,x,y;
vector<int>RoziIsShit[250002];
vector<int>RoseCost[250002];
struct nod
{
    int a,b,cost;
};
nod v[500001];
bool test(nod a, nod b)
{
    if(a.a==b.a && a.b==b.b)
        return a.cost<b.cost;
    if(a.a==b.a)
        return a.b<b.b;
    return a.a<b.a;
}
bool viz[250002];
bool bfs(int dist)
{
    deque<int>d;
    d.push_back(x);
    memset(viz,0,n+1);
    viz[x]=1;
    while(!d.empty())
    {
        for(int i=0;i<RoziIsShit[d.front()].size();++i)
            if(viz[RoziIsShit[d.front()][i]]==0 && RoseCost[d.front()][i]<=dist)
                viz[RoziIsShit[d.front()][i]]=1,d.push_back(RoziIsShit[d.front()][i]);
        d.pop_front();
    }
    return viz[y];
}
int main()
{
    f>>n>>m>>x>>y;
    for(int i=1;i<=m;++i)
        f>>v[i].a>>v[i].b>>v[i].cost;
    sort(v+1,v+m+1,test);
    for(int i=1;i<=m;++i)
        if(v[i].a!=v[i].b)
            if(v[i].a!=v[i-1].a || v[i].b!=v[i-1].b){
                RoziIsShit[v[i].a].push_back(v[i].b);
                RoseCost[v[i].a].push_back(v[i].cost);
            }
    int b=1;
    int e=1000;
    int cmin=1001;
    while(b<=e)
    {
        int m=(b+e)/2;
        if(bfs(m)==1)
            cmin=m,e=m-1;
        else
            b=m+1;
    }
    g<<cmin;
    return 0;
}