#include <cstdio>
#include <fstream>
#include <vector>
#include <algorithm>

#define x first
#define y second
#define NMAX 250007

const int BUFFER_SIZE = 1 << 16;

using namespace std;

int H[NMAX], T[NMAX];
int n, m, X, Y;
vector< pair< int, int > > v[1007];

class InputReader {
    public:
        InputReader() {}
        InputReader(const char* filename) {
            file = fopen(filename, "r");
            cursor = 0;
            fread(buffer, BUFFER_SIZE, 1, file);
        }
        inline InputReader & operator >> (int &n) {
            n = 0;
            while(!isdigit(buffer[cursor])) {
                advance();
            }
            while(isdigit(buffer[cursor])) {
                n = n * 10 + buffer[cursor] - '0';
                advance();
            }
            return *this;
        }
    private:
        int cursor;
        char buffer[BUFFER_SIZE];
        FILE* file;
        inline void advance() {
            ++ cursor;
            if(cursor == BUFFER_SIZE) {
                cursor = 0;
                fread(buffer, BUFFER_SIZE, 1, file);
            }
        }
};

void unite(int x, int y){
    if(H[x] == H[y]){
        ++ H[x];
        T[y] = x;
    }
    else
        if(H[x] < H[y])
            T[x] = y;
        else
            T[y] = x;
}

inline int father(int x){
    if(x == T[x])
        return x;
    return father(T[x]);
}

int main(){
    InputReader in("pscnv.in");
    freopen("pscnv.out", "w", stdout);
    in >> n >> m >> X >> Y;
    for(int i = 1; i <= m; ++i){
        int a = 0, b = 0, c = 0;
        in >> a >> b >> c;
        v[c].push_back(make_pair(a, b));
        T[i] = i;
        H[i] = 1;
    }
    int i;
    for(i = 1; father(X) != father(Y); ++i){
        for(vector< pair<int, int> >::iterator it = v[i].begin(); it != v[i].end(); ++it){
            int Tx = father(it->x), Ty = father(it->y);
            if(Tx != Ty)
                unite(Tx, Ty);
        }
    }
    printf("%d\n", i - 1);
    return 0;
}