#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
vector< int > G[NMAX];
int n,m,sursa;
bitset <NMAX> b;
ifstream f("dfs.in");
ofstream g("dfs.out");
int nrconex;
void DFS(int x){
    for(auto it:G[x])if(!b[it])b[it]=true,DFS(it);
}
int main()
{
    f>>n>>m>>sursa;
    for(int i=1,x,y;i<=m;i++){
        f>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!b[i]) ++nrconex,DFS(i);
    g<<nrconex;
    return 0;
}