#include<cstdio>
#include<vector>
#include<queue>
using namespace std;
int j,nr,m,x,y,s,i,n,b[100002];
vector < int > h[100002];
queue < int > cc;
int main()
{
freopen("dfs.in","r",stdin);
freopen("dfs.out","w",stdout);
scanf("%d",&n);
scanf("%d",&m);
scanf("%d",&s);
for(i=1;i<=m;i++)
{
	scanf("%d",&x);
	scanf("%d",&y);
	h[x].push_back(y);
	h[y].push_back(x);
}
for(j=1;j<=n;j++)
if(b[j]==0)
{
	s=j;
	cc.push(s);
	nr++;
	b[s]=0;
	while(!cc.empty())
	{
		x=cc.front();
		for(i=0;i<h[x].size();i++)
			if(b[h[x][i]]==0)
			{
				b[h[x][i]]=1;
				cc.push(h[x][i]);
			}
		cc.pop();
	}
}
printf("%d\n",nr);
return 0;
}