#include <fstream>
#include <vector>

using namespace std;

ifstream f("dfs.in");
ofstream gg("dfs.out");
int n,m,s,v[100005],p[100005],cc=1;

vector <int>g[100005];

void dfs(int nod){
    v[nod]=1;
    p[nod]=cc;
    for(auto a:g[nod]){
        if(v[a]!=1){
            dfs(a);
            p[a]=cc;
        }
    }
}

int main()
{
    int x,y;
    f>>n>>m>>s;
    for(int i=1;i<=m;i++){
        f>>x>>y;
        if(x!=y){
            g[x].push_back(y);
            g[y].push_back(x);
        }
    }
    dfs(1);

    for(int i=2;i<=n;i++){
        if(p[i]==0){
            cc++;
            dfs(i);
        }
    }
    gg<<cc;
}