#include <fstream>
#include <algorithm>
#include <cstring>
#include <vector>
#include <queue>
#include <utility>
using namespace std;

int pos,sz,x,y,n,m;
vector< pair<int,int> > G[250001];

struct comp
{
    bool operator()(const pair<int,int>& a,const pair<int,int>& b)
    {
        return a.second > b.second;
    }
};

class InputReader
{
    public:
        InputReader() {}

        InputReader(const char *file_name)
        {
            input_file = fopen(file_name, "r");
            cursor = 0;
            fread(buffer, SIZE, 1, input_file);
        }

        inline InputReader &operator >>(int &n)
        {
            while (buffer[cursor] < '0' || buffer[cursor] > '9')
                advance();

            n = 0;
            while ('0' <= buffer[cursor] && buffer[cursor] <= '9')
            {
                n = n * 10 + buffer[cursor] - '0';
                advance();
            }

            return *this;
        }

    private:
        FILE *input_file;
        static const int SIZE = 1 << 17;
        int cursor;
        char buffer[SIZE];

        inline void advance()
        {
            ++cursor;
            if (cursor == SIZE)
            {
                cursor = 0;
                fread(buffer, SIZE, 1, input_file);
            }
        }
};

priority_queue< pair<int,int>, vector< pair<int,int> >, comp> Q;

int dist[250001];

void Dijkstra()
{
    memset(dist,0x3f3f3f3f,sizeof dist);
    Q.push(make_pair(x,-1));
    int u,d,nd;
    bool ok = 0;
    while (!Q.empty())
    {
        u = Q.top().first;
        d = Q.top().second;
        Q.pop();
        if (ok && u == y) return;
        for (vector< pair<int,int> >::iterator it = G[u].begin(); it != G[u].end(); it++)
        {
            nd = max (d,it->second);
            if (dist[it->first] > nd)
            {
                dist[it->first] = nd;
                Q.push(make_pair(it->first,nd));
            }
        }
        ok = 1;
    }
}

int main()
{
    InputReader fin("pscnv.in");
    ofstream fout("pscnv.out");

    fin >> n >> m >> x >> y;

    int a,b,c;
    for (int i = 1; i <= m; i++)
    {
        fin >> a >> b >> c;
        G[a].push_back(make_pair(b,c));
    }

    Dijkstra();

    fout << dist[y];
}