#include <bits/stdc++.h>
using namespace std;
int done[5001] = {0};
vector<int> adj[5001];
int income[5001][5001];
long long ans = 0;
stack<int> stack1;
void DFSUtil1(long long u, vector<bool> &visited, long long p) {
  visited[u] = true;
  long long i;
  for (i = 0; i < adj[u].size(); i++)
    if (visited[adj[u][i]] == false && done[adj[u][i]] == 0)
      DFSUtil1(adj[u][i], visited, u);
  stack1.push(u);
}
void DFSUtil2(long long u, vector<long long> adj[], vector<bool> &visited,
              long long p, vector<long long> *temp) {
  visited[u] = true;
  temp->push_back(u);
  long long i;
  for (i = 0; i < adj[u].size(); i++)
    if (visited[adj[u][i]] == false && done[adj[u][i]] == 0)
      DFSUtil2(adj[u][i], adj, visited, u, temp);
}
void SCC(long long s) {
  long long u, i, j;
  vector<bool> visited(s, false);
  for (u = 0; u < s; u++)
    if (visited[u] == false && done[u] == 0) DFSUtil1(u, visited, -1);
  vector<long long> trps[s];
  for (i = 0; i < s; i++) {
    for (j = 0; j < adj[i].size(); j++) {
      trps[adj[i][j]].push_back(i);
    }
  }
  for (i = 0; i < visited.size(); i++) visited[i] = false;
  while (!stack1.empty()) {
    long long v = stack1.top();
    stack1.pop();
    if (visited[v] == false && done[v] == 0) {
      vector<long long> *temp = new vector<long long>;
      vector<long long> in;
      DFSUtil2(v, trps, visited, -1, temp);
      for (i = 0; i < temp->size(); i++) {
        for (j = 0; j < temp->size(); j++) income[(*temp)[i]][(*temp)[j]] = 0;
      }
      int l = 0;
      for (i = 0; i < temp->size(); i++) {
        for (j = 0; j < 5001; j++) {
          if (income[(*temp)[i]][j] == 1) l = 1;
        }
      }
      if (l == 0) ans++;
    }
  }
}
void dfs(int n) {
  done[n] = 1;
  for (int i = 0; i < adj[n].size(); i++) {
    if (done[adj[n][i]] != 1) dfs(adj[n][i]);
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  long long a, s, b, c, i, j, k, l, m, t, x, y, n, z;
  cin >> n >> m >> s;
  for (i = 0; i < 5001; i++)
    for (j = 0; j < 5001; j++) income[i][j] = 0;
  for (i = 0; i < m; i++) {
    cin >> x >> y;
    x--;
    y--;
    adj[x].push_back(y);
    income[y][x] = 1;
  }
  s--;
  dfs(s);
  SCC(n);
  cout << ans << endl;
}
