#include <bits/stdc++.h>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int i,j,n,x,s,y,poz,viz[100005],nr,m,nr2,p;
vector<int> v[100001];
queue<int> q;
int main()
{ fin>>n>>m>>poz;
  for(i=1;i<=m;i++)
  {fin>>x>>y;
   v[x].push_back(y);
   v[y].push_back(x);
  }
  p=1;
  while(nr2<n)
  { while(viz[p]==1 && p<=n)
         p++;
    if(p<=n) q.push(p);

   while(!q.empty())
  {
   j=q.front();
   viz[j]=1;
   nr2++;
   for(i=0;i<v[j].size();i++)
       if(viz[v[j][i]]==0) q.push(v[j][i]);
    q.pop();
  }
   nr++;
  }
  fout<<nr;
    return 0;
}