#include <fstream>
#include <vector>
#include <queue>

using namespace std;

const char InFile[]="dfs.in";
const char OutFile[]="dfs.out";

const int MaxN = 100005;

ifstream fin(InFile);
ofstream fout(OutFile);

int N,M,S,x,y,k;
vector<int> a[MaxN];
int	d[MaxN];

void bfs(int S,int k)
{
	d[S]=0;
	queue<int> q;
	q.push(S);
	while(!q.empty())
	{
		int nod=q.front();
		q.pop();
		for(register int i=0;i<(int)a[nod].size();++i)
		{
			if(d[a[nod][i]]==-1)
			{
				d[a[nod][i]]=k;
				q.push(a[nod][i]);
			}
		}
	}
}

int main()
{

	fin>>N>>M>>S;
	for(register int i=0;i<M;++i)
	{
		fin>>x>>y;
		a[x].push_back(y);
		a[y].push_back(x);
	}
	fin.close();
	for(register int i=1;i<=N;++i)
	{
		d[i]=-1;
	}

	k=0;
	for(register int i=1;i<=N;++i)
	{
		if(d[i]==-1)
		{
			++k;
			bfs(i,k);
		}
	}

	fout<<k;
	fout.close();
	return 0;
}