#include <cstdio>
#include <queue>
#include <vector>
#include <cstring>
#include <algorithm>
#define pb push_back
#define pf push_front
#define mp make_pair
using namespace std;
const int kmax=1004,nmax=250004,DIM=100000;
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;
    }
}
deque<int>lista[kmax];
vector< pair<int,int> > adj[nmax];
int n,m,x,y;
int cost[nmax],vis[nmax];
void dijkstra()
{
    for(int ind=0;ind<=1000;ind++)
    {
        while(!lista[ind].empty())
        {
            int nod=lista[ind].front();
            lista[ind].pop_front();
            if(cost[nod]<ind) continue;
            for(vector< pair<int,int> >::iterator it=adj[nod].begin();it!=adj[nod].end();++it)
            {
                if(cost[(*it).first]>max(cost[nod],(*it).second))
                {
                    cost[(*it).first]=max(cost[nod],(*it).second);
                    lista[cost[(*it).first]].pb((*it).first);
                }
            }
        }
    }
}
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;
    lista[0].pb(x);
    for(int i=1;i<=m;i++)
    {
        int a,b,c;
        citeste(a),citeste(b),citeste(c);
        if(a==b) continue;
        adj[a].pb(mp(b,c));
    }
    dijkstra();
    printf("%d\n",cost[y]);
}