#include <cstdio>

int  i, j, n, tall, head, cur, u, s, m, x, y, v, d[5000], queue [5000];
bool  a[5000][5000], used[5000];

void push (int s)
{
  queue[head]=s;
  head++;
}
int pop()
{
  tall++;
  return queue[tall - 1];
}
int main()
{
  freopen("maxmin.in", "r", stdin);
  freopen("maxmin.out", "w", stdout);
  scanf("%d%d%d\n", &n, &m, &s);
  s--;
  for ( i = 0; i < n; i++)
    for ( j = 0; j < n; j++)
      a[i][j] = false;
  for (i = 0; i < m; i++)
  {
    scanf("%d%d", &x, &y);
    a[y - 1][x - 1] = true;
  }
  for ( i = 0; i < n; i++)
    used[i]= false;
  used[s] = true;
  d[s] = 0;
  push(s);
  while (tall < head)
  {
    cur = pop();
    for (u = 0; u < n; u++)
    {
      if ((a[cur][u] == true) &&  !used[u])
      {
        push(u);
        used[u] = true;
        d[u] = d[cur] + 1;
      }
    }
  }
  v = d[s];
  for ( i = 0; i < n; i++)
    if (d[i] > v)
      v = d[i];
  printf("%d", v);
  return 0;
}