#include <list>
#include <fstream>

using namespace std;

#define f first
#define s second

ifstream fin("pscnv.in");
ofstream fout("pscnv.out");

int a,b,c,d,fv[500010],ans,x,y,ls,ld,mij,n,m,i;
list< pair<int,int> > G[500010];

void DF( int nod )
{
    fv[ nod ] = mij;
    for( auto it : G[ nod ] )
        if( it.s <= mij && fv[ it.f ] != mij )
            DF( it.f );
}

int main()
{
    fin>>n>>m>>a>>b;
    for( i = 1 ; i <= m ; i++ )
    {
        fin>>x>>y>>c;
        G[ x ].push_back( { y , c } );
    }
    ls = 1;
    ld = 1000;
    while( ls <= ld )
    {
        mij = ls + ( ld - ls ) / 2;
        DF( a );
        if( fv[ b ] == mij )
        {
            ld = mij - 1;
            ans = mij;
        }
        else
        {
            ls = mij + 1;
        }
    }
    fout<<ans;


return 0;
}