#include <cstdio>
#include <vector>
#include <queue>
 
using namespace std;
 
const int DIM = (1 << 17);
 
int n, m, src, dst, x, y, z;
 
vector <pair <int, int>> g[250005];
bool viz[250005];
 
char nxt() {
  static char buff[DIM];
  static int bp = DIM;
  if(bp == DIM) {
    fread(buff, 1, DIM, stdin);
    bp = 0;
  }
  return buff[bp++];
}
 
void read(int &x) {
  static char ch;
  x = 0;
  do {
    ch = nxt();
  } while(ch < '0' || '9' < ch);
  do {
    x = x * 10 + ch - '0';
    ch = nxt();
  } while('0' <= ch && ch <= '9');
}
 
bool bfs(int lim) {
  queue <int> q;
  for(int i = 1; i <= n; i++)
    viz[i] = 0;
  viz[src] = 1;
  q.push(src);
  while(!q.empty()) {
    int nod = q.front();
    q.pop();
    for(auto &fiu : g[nod]) {
      if(fiu.second <= lim && !viz[fiu.first]) {
        q.push(fiu.first);
        viz[fiu.first] = 1;
      }
    }
  }
  return viz[dst];
}
 
int main() {
  freopen("pscnv.in", "r", stdin);
  freopen("pscnv.out", "w", stdout);
  read(n), read(m), read(src), read(dst);
  for(; m; m--) {
    read(x), read(y), read(z);
    g[x].push_back({y, z});
  }
  int st = 1, dr = 1000, mid;
  while(st <= dr) {
    mid = (st + dr) >> 1;
    if(bfs(mid))
      dr = mid - 1;
    else
      st = mid + 1;
  }
  printf("%d", st);
  return 0;
}