#include <cstdio>
#include <cstring>
#include <vector>
#include <cstdlib>
#define NMAX 200200
#define CMAX 200200
#define max(a, b) ((a) > (b) ? (a):(b))
#define mod(a) ( ((a) >= 200020) ? ((a)-CMAX):(a) )

using namespace std;

vector<int> A[NMAX];
vector<int> K[NMAX];
int N, M, X, Y, Kmin, F[NMAX], C[CMAX+10], G[NMAX];
char buf[NMAX*50];

int main()
{
        int i, j, c, k, hi, lo, mij, m = 0, p1, p2, ok, nod;

        FILE *f = fopen("pscnv.in", "rt");
        setbuffer(f,buf,sizeof(buf));
        fscanf(f,"%d %d %d %d", &N, &M, &X, &Y);

        while (M--)
        {
                fscanf(f,"%d %d %d", &i, &j, &c);
                G[i]++; G[j]++;
                A[i].push_back(j);
                A[j].push_back(i);
                K[i].push_back(c);
                K[j].push_back(c);
                m = max(m, c);
        }

        for (lo = 0, hi = m; lo <= hi; lo++)
        {
                mij = (hi+lo)>>1;
                memset(C, 0, sizeof(C));
                C[p1 = 0] = X; p2 = 1;
                memset(F, 0, sizeof(F));
                for (ok = 0, F[X] = 1; p1 != p2 && ok == 0; )
                {
                        for (nod = C[p1], m = G[nod], i = 0; i < m && ok == 0; i++)
                            if (F[ A[nod][i] ] == 0 && K[nod][i] <= mij)
                                F[ A[nod][i] ] = 1, C[p2] = A[nod][i],
                                ok = (A[nod][i] == Y), p2 = mod(p2+1);
                        p1 = mod(p1+1);
                }
                if (ok == 1) hi = mij-1, Kmin = mij;
                else lo = mij+1;
        }

        freopen("pscnv.out", "w", stdout);
        printf("%d\n", Kmin);

        return 0;
        
}