#include<bits/stdc++.h>

#define forn(i, n) for (int i = 0 ; i < int(n) ; i++)

#define fore(i, s, t) for (int i = s ; i < (int)t ; i++)

#define fi first

#define se second

#define all(x) x.begin(),x.end()

#define pf2(x,y) printf("%d %d\n",x,y)

#define pf(x) printf("%d\n",x)

#define each(x) for(auto it:x)  cout<<it<<endl;

#define pi pair<int,int>

using namespace std;

typedef long long ll;

const int maxn=1e6+5;

const int maxm=2e5+5;

const int inf=1e9;

int head[maxn],ver[maxm],nex[maxm],tot;

void inline AddEdge(int x,int y){

	ver[++tot]=y,nex[tot]=head[x],head[x]=tot;

}

int dfn[maxn],low[maxn],num,sccnum,scc[maxn],s[maxn],d[maxn],top;

void Tarjan(int x){

	low[x]=dfn[x]=++num;

	s[++top]=x;

	for(int i=head[x];i;i=nex[i]){

		int y=ver[i];

		if(!dfn[y]) {

			Tarjan(y);

			low[x]=min(low[x],low[y]);

		}

		else if(!scc[y]) low[x]=min(low[x],dfn[y]);//说明找到了一条反祖边

	}

	if(low[x]==dfn[x]) {

		sccnum++;

		while(s[top]!=x) {

			scc[s[top]]=sccnum;

			top--;

		}

		scc[s[top]]=sccnum;

		top--;

	}

}

int main(){

	int n,m,s;

	cin>>n>>m>>s;

	for(int i=0;i<m;i++){

		int x,y;

		scanf("%d%d",&x,&y);

		AddEdge(x,y);

	}

	for(int i=1;i<=n;i++)

		if(!dfn[i]) Tarjan(i);

	for(int x=1;x<=n;x++){

		for(int i=head[x];i;i=nex[i]){

			int y=ver[i];

			if(scc[x]!=scc[y]){

				d[scc[y]]++;

			}

		}

	}

	int ans=0;

	for(int i=1;i<=sccnum;i++)

		if(!d[i] && i!=scc[s]) ans++;

	cout<<ans<<endl;

}