codeforces#999 E. Reachability from the Capital（图论加边）

#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int maxn = 5e3 + 5;
ll mod =  998244353;
vector<int>ve[maxn];
int vis[maxn],fla[maxn];
void dfs(int x){
    vis[x]=1;
    for(int i=0;i<ve[x].size();i++){
        int v=ve[x][i];
        if(vis[v]==0)dfs(v);
    }
}
int main()
{
    int n,m,s,ans=0;
    scanf("%d %d %d",&n,&m,&s);
    for(int i=1;i<=m;i++){
        int a,b;
        scanf("%d %d",&a,&b);
        ve[a].push_back(b);
    }
    dfs(s);
    for(int i=1;i<=n;i++)
        if(vis[i]==0)fla[i]=1;
    for(int i=1;i<=n;i++){
        if(fla[i]==0)continue;
        for(int j=1;j<=n;j++)vis[j]=0;
        dfs(i);
        for(int j=1;j<=n;j++)
            if(j!=i&&vis[j])fla[j]=0;
    }
    for(int i=1;i<=n;i++)if(fla[i])ans++;
    printf("%d\n",ans);
    return 0;
}