#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>
#include <queue>
#define DN 250005
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define un unsigned
using namespace std;

int minim[DN];
queue<pair<int,int> > q;
vector<pair<int,int> > list[DN];

int main()
{
    int n,m,x,y;
    ifstream f("pscnv.in");
    ofstream g("pscnv.out");
    f>>n>>m>>x>>y;
    for(;m;--m)
    {
        int x,y,c;
        f>>x>>y>>c;
        list[x].pb(mp(y,c));
    }
    memset(minim,127,sizeof(minim));
    q.push(mp(x,0));
    minim[x]=0;
    while(q.size())
    {
        int nod=q.front().f;
        int cost=q.front().s;
        q.pop();

        for(un int i=0;i<list[nod].size();++i)
        {
            int next_nod=list[nod][i].f;
            int next_cost=list[nod][i].s;
            if( minim[next_nod] > max(cost,next_cost))
                {
                    minim[next_nod]=max(cost,next_cost);
                    q.push(mp(next_nod,minim[next_nod]));
                }
        }
    }
    g<<minim[y];

    return 0;
}