#include <cstdio>

const int maxn = 250001;

FILE *in = fopen("pscnv.in","r"), *out = fopen("pscnv.out","w");

struct graf
{
    int nod;
    short cost;
    graf *next;
};

int n, m, x, y;

graf *a[maxn];

void add(int to, int nod, short cost)
{
    graf *q = new graf;

    q->next = a[to];
    q->nod = nod;
    q->cost = cost;
    a[to] = q;
}

void read()
{
    fscanf(in, "%d %d %d %d", &n, &m, &x, &y);

    int p, q;
    short c;
    for ( int i = 1; i <= m; ++i )
    {
        fscanf(in, "%d %d %hd", &p, &q, &c);

        if ( p != q )
            add(p, q, c);
    }
}

struct tail
{
    int nod;
    tail *next;
};

//char viz[maxn];

int check(int k)
{
    tail *p = new tail;
    tail *u = new tail;

    char viz[maxn] = {0};

    p->next = NULL;
    p->nod = x;

    u = p;

    while ( p )
    {
        graf *q = a[ p->nod ];

        while ( q )
        {
            if ( !viz[q->nod] && q->cost <= k )
            {
                tail *t = new tail;

                t->next = NULL;
                t->nod = q->nod;
                u->next = t;
                u = t;

                if ( u->nod == y )
                    return 1;

                viz[u->nod] = 1;
            }
            q = q->next;
        }
        tail *t = p;
        p = p->next;

        delete t;
    }

    return 0;
}

int main()
{
    read();

    for ( int i = 1; i <= 1000; ++i )
        if ( check(i) )
        {
            fprintf(out, "%d\n", i);
            return 0;
        }

	return 0;
}