#include <cstdio>
#include <queue>
#include <vector>
#include <cstring>
#include <algorithm>
#define pb push_back
#define mp make_pair
using namespace std;
const int nmax=250004,DIM=50000;
int poz=DIM-1;
char buff[DIM];
void citeste(int &nr)
{
    nr=0;
    while(!('0'<=buff[poz]&&buff[poz]<='9'))
    {
        if(++poz==DIM) fread(buff,1,DIM,stdin),poz=0;
    }
    while('0'<=buff[poz]&&buff[poz]<='9')
    {
        nr=nr*10 + buff[poz]-'0';
        if(++poz==DIM) fread(buff,1,DIM,stdin),poz=0;
    }
}
queue< int >dj;
vector< pair<int,int> > adj[nmax];
int n,m,x,y;
int cost[nmax],vis[nmax];
void dijkstra()
{
    dj.push(x);
    while(!dj.empty())
    {
        int nod=dj.front();
        vis[nod]=0;
        dj.pop();
        for(vector< pair<int,int> >::iterator it=adj[nod].begin();it!=adj[nod].end();++it)
        {
            int vc=(*it).first,edg=(*it).second;
            if(cost[vc]>max(cost[nod],edg))
            {
                cost[vc]=max(cost[nod],edg);
                if(vis[vc]==0)
                {
                    dj.push(vc);
                    vis[vc]=1;
                }
            }
        }
    }
}
int main()
{
    freopen ("pscnv.in","r",stdin);
    freopen ("pscnv.out","w",stdout);
    citeste(n),citeste(m),citeste(x),citeste(y);
    for(int i=1;i<=n;i++) cost[i]=0x3f3f3f3f;
    cost[x]=0;
    for(int i=1;i<=m;i++)
    {
        int a,b,c;
        citeste(a),citeste(b),citeste(c);
        adj[a].pb(mp(b,c));
    }
    dijkstra();
    printf("%d\n",cost[y]);
}