#include <cstdio>
#include <vector>
#include <queue>

#define DIM 100
#define INF 100000
#define NMAX 250005
#define max(a,b) a>b?a:b

using namespace std;

char buff[DIM+5];

int best[NMAX];
int n,m,x,y,z,nod1,nod2,poz=DIM-1;

queue <int>q;
vector <pair <int ,int > >v[NMAX];
vector <pair <int ,int > >::iterator it;

inline void citeste(int &numar)
{
    numar=0;
    while (buff[poz]<'0' || buff[poz]>'9')
       if (poz++==DIM)poz=0,fread(buff,1,DIM,stdin);

    while (buff[poz]>='0' && buff[poz]<='9')
      {
          numar=numar*10+buff[poz++]-'0';
          if (poz==DIM)poz=0,fread(buff,1,DIM,stdin);
      }
}
int main()
{
    freopen("pscnv.in","r",stdin);
    freopen("pscnv.out","w",stdout);

    citeste(n);
    citeste(m);
    citeste(nod1);
    citeste(nod2);

    for (int i=1;i<=n;i++)best[i]=INF;
    for (int i=1;i<=m;i++)
     {
        citeste(x);
        citeste(y);
        citeste(z);
        v[x].push_back(make_pair(y,z));
     }
    best[nod1]=0;
    q.push(nod1);
    while (q.size())
     {
          int nod=q.front();
          q.pop();

          for (it=v[nod].begin();it!=v[nod].end();it++)
            if (max(best[nod],(*it).second)<best[(*it).first])
             {
                 q.push((*it).first);
                 best[(*it).first]=max(best[nod],(*it).second);
             }
     }
    printf("%d",best[nod2]);

    fclose(stdin);
    fclose(stdout);
}