#include <iostream>
#include <fstream>
#include <vector>

using namespace std;
int n,m,cont;
vector<int> a[1000000];
int viz[1000000];

ifstream f("dfs.in");
ofstream g("dfs.out");

void DFS(int x){
    if(x>n)return;
    else {
        for(auto y:a[x]){
            if(viz[y]==0){
                viz[y]=1;
                DFS(y);
                cont++;
            }
        }
    }
}

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

    DFS(1);
    g<<cont;
    return 0;
}