#include <cstdio>
#include <vector>
#include <bitset>
#include <algorithm>

#define DIM 256000
using namespace std;

int N, M, st, fi, X, Y, Z;
vector <pair <int, int> > List[DIM];
bitset <DIM> Marked;

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);
            }
        }
};

void DFS (int nod, int cost)
{
    Marked[nod] = 1;

    vector <pair <int, int> > :: iterator i;
    for (i = List[nod].begin(); i != List[nod].end(); i ++)
    {
        pair <int, int> vec = *i;

        if(!Marked[vec.first] && vec.second <= cost)
            DFS(vec.first, cost);
    }

    return;
}

int main()
{
    //freopen ("pscnv.in" ,"r", stdin );
    InputReader fin("pscnv.in");
    freopen ("pscnv.out","w", stdout);

    //scanf ("%d %d", &N , &M );
    //scanf ("%d %d", &st, &fi);
    fin >> N >> M;
    fin >> st >> fi;

    for (int i = 1; i <= M; i ++)
    {
        //scanf ("%d %d %d", &X, &Y, &Z);
        fin >> X >> Y >> Z;
        List[X].push_back(make_pair(Y, Z));
    }

    int st = 1, dr = 1000, mid;
    while (st <= dr)
    {
        mid = st + ((dr - st) >> 1);
        Marked.reset();

        DFS (st, mid);

        if (Marked[fi])
            dr = mid - 1;
        else
            st = mid + 1;
    }

    printf ("%d\n", st);

    fclose (stdin );
    fclose (stdout);

    return 0;
}