#include<bits/stdc++.h>

using namespace std;

vector<vector<int>> g;
vector<int> ord, used, u;

void dfs(int v)
{
    if(used[v])
    {
        return;
    }
    used[v] = true;
    u[v] = true;
    for(auto i : g[v])
    {
        dfs(i);
    }
}

void dfs1(int v)
{
    if(used[v] || u[v])
    {
        return;
    }
    used[v] = true;
    for(auto i : g[v])
    {
        dfs1(i);
    }
    ord.push_back(v);
}

void dfs2(int v)
{
    if(used[v] || u[v])
    {
        return;
    }
    used[v] = true;
    for(auto i : g[v])
    {
        dfs2(i);
    }
}


int main()
{
    int n, m, s;
    cin >> n >> m >> s;
    g.resize(n + 1);
    used.resize(n + 1);
    u.resize(n + 1);
    for(int i = 0; i < m; ++i)
    {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
    }
    dfs(s);
    used.assign(n + 1, 0);
    for(int i = 1; i <= n; ++i)
    {
        if(!used[i] && !u[i])
        {
            dfs1(i);
        }
    }
    reverse(ord.begin(), ord.end());
    int ans = 0;
    used.assign(n + 1, 0);
    for(auto i : ord)
    {
        if(!used[i] && !u[i])
        {
            dfs2(i);
            ++ans;
        }
    }
    cout << ans;
}