#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
using namespace std;
const long long llmx = 9223372036854775807;
const int inf = 1e9;
struct kek {
  int x;
  int y;
  long long c;
};
bool isPrime(long long x) {
  if (x == 1) {
    return false;
  }
  for (long long i = 2; i <= (long long)sqrt(x); i++) {
    if (x % i == 0) {
      return false;
    }
  }
  return true;
}
long long gcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
long long factorial(long long x) {
  long long sum = 1;
  for (long long i = 1; i <= x; i++) {
    sum *= i;
  }
  return sum;
}
int toint(string s) {
  int x = 0;
  for (int i = 0; i < (int)s.length(); i++) {
    x *= 10;
    x += (s[i] - '0');
  }
  return x;
}
string tostr(int x) {
  if (x == 0) {
    return "0";
  }
  string s = "";
  bool f = x < 0;
  x = abs(x);
  while (x != 0) {
    s += (x % 10) + '0';
    x /= 10;
  }
  string t = "";
  if (f) {
    t = "-";
  }
  for (int i = s.length() - 1; i >= 0; i--) {
    t += s[i];
  }
  return t;
}
long long bpow(long long a, long long b) {
  if (b == 0) {
    return 1;
  } else {
    if (b % 2 == 1) {
      return bpow(a, b - 1) * a;
    } else {
      long long r = bpow(a, b / 2);
      return r * r;
    }
  }
}
bool foo(int x) {
  while (x != 0) {
    int t = x % 10;
    if (t != 4 && t != 7) {
      return false;
    }
    x /= 10;
  }
  return true;
}
vector<int> g[5005];
int c[5005];
vector<int> b;
bool us[5005];
void dfs1(int x) {
  us[x] = true;
  c[x] = 0;
  for (int i = 0; i < g[x].size(); i++) {
    int y = g[x][i];
    if (!us[y]) {
      dfs1(y);
    }
  }
}
void dfs2(int x) {
  us[x] = true;
  for (int i = 0; i < g[x].size(); i++) {
    int y = g[x][i];
    if (!us[y]) {
      dfs2(y);
    }
  }
  b.push_back(x);
}
void dfs(int x, int cl) {
  us[x] = true;
  if (c[x] == -1) {
    c[x] = cl;
  }
  for (int i = 0; i < g[x].size(); i++) {
    int y = g[x][i];
    if (!us[y]) {
      dfs(y, cl);
    }
  }
}
int main() {
  int n, m, s;
  cin >> n >> m >> s;
  for (int i = 0; i < m; i++) {
    int x, y;
    cin >> x >> y;
    g[x].push_back(y);
  }
  for (int i = 1; i <= n; i++) {
    c[i] = -1;
  }
  dfs1(s);
  for (int i = 1; i <= n; i++) {
    us[i] = false;
  }
  for (int i = 1; i <= n; i++) {
    if (!us[i]) {
      dfs2(i);
    }
  }
  int cl = 0;
  for (int i = 1; i <= n; i++) {
    us[i] = false;
  }
  reverse(b.begin(), b.end());
  for (int i = 0; i < b.size(); i++) {
    int x = b[i];
    if (!us[x] && c[x] == -1) {
      cl++;
      dfs(x, cl);
    }
  }
  cout << cl;
  return 0;
}
