#include <cstdio>
#include <vector>
#include <queue>
using namespace std;
int n,m,in,sf,x,y,k,i,v[250005],pr[250005];
vector <int> w[250005];
vector <int> l[250005];
queue <int> q;
int main()
{
    FILE *f=fopen("pscnv.in","r");
    FILE *g=fopen("pscnv.out","w");
    fscanf(f,"%d%d%d%d",&n,&m,&in,&sf);
    for(i=1; i<=n; i++)
    {
        v[i]=1005;
        w[i].push_back(0);
        l[i].push_back(0);
    }
    for(i=1; i<=m; i++)
    {
        fscanf(f,"%d%d%d",&x,&y,&k);
        w[x].push_back(y);
        w[x][0]++;
        l[x].push_back(k);

        w[y].push_back(x);
        w[y][0]++;
        l[y].push_back(k);
    }
    v[in]=0;
    pr[in]=1;
    q.push(in);
    while(!q.empty())
    {
        x=q.front();
        q.pop();
        pr[x]=0;
        for(i=1; i<=w[x][0]; i++)
        {
            y=w[x][i];
            if(v[y]>max(v[x],l[x][i]))
            {
                v[y]=max(v[x],l[x][i]);
                if(pr[y]==0)
                {
                    q.push(y);
                    pr[y]=1;
                }
            }
        }
    }
    fprintf(g,"%d\n",v[sf]);
    fclose(f); fclose(g);
    return 0;
}