#include <fstream>
#include <bitset>
#include <list>
#include <cstring>

using namespace std;

list<pair<int,int> >G[250010];
int n,m,x,y,c,i,j,ls,ld,mij,a,b,ans,viz[250010];

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

void DF( int nod )
{
    viz[ nod / 32 ] |= ( 1 << ( nod % 32 ) );
    for( auto it : G[ nod ] )
    {
        if( ( viz[ it.first / 32 ] ^ ( 1 << ( it.first % 32 ) ) ) && it.second <= mij )
            DF( it.first );
    }
}

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 ) / 2;
        for( i = 0 ; i <= n / 32 + 2 ; i++ )
            viz[ i ] = 0;
        DF( a );
        if( ls == ld )
        {
            if( viz[ b ] == 1 )
                fout<<min(ans,mij);
            else
                fout<<ans;
            return 0;
        }
        if( viz[ b / 32 ] ^ ( 1 << ( b % 32 ) ) )
            ld = mij - 1,ans = mij;
        else
            ls = mij + 1;
    }
    fout<<ans;

return 0;
}