#include <bits.h>
#include<iostream>
#include <vector>
#include <fstream>
using namespace std;

vector<int> L[100001];
int vis[100001];
ifstream fin("dfs.in");
ofstream fout("dfs.out");

void dfs(int node) {
    vis[node]=1;
    for (auto vec: L[node]) {
        if (vis[vec]==0) {
            dfs(vec);
        }
    }
}

int main() {

    int n,m;
    fin>>n>>m;
    for (int i=1;i<=m;i++) {
        int x,y;
        fin>>x>>y;
        L[x].push_back(y);
        L[y].push_back(x);
    }
    int nr=0;
    for (int i=1;i<=n;i++) {
        if (vis[1]==0) {
            nr++;
            dfs(i);
        }
    }
    fout<<nr;

    return 0;
}