#include <bits/stdc++.h>
using namespace std;

void dfs(int node, vector<vector<int>> &adj, vector<bool> &visited) {
    visited[node] = true;
    for (int i = 0; i < adj[node].size(); i++) {
        if (!visited[adj[node][i]])
            dfs(adj[node][i], adj, visited);
    }
}

int main() {
    ifstream fin("dfs.in");
    ofstream fout("dfs.out");

    int n, m, x, y, comp = 1;

    fin >> n >> m;

    vector<vector<int>> adj(n + 1);
    vector<bool> visited(n + 1, false);

    for (int i = 0; i < m; i++) {
        fin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    
    dfs(1, adj, visited);

    for (int i = 2; i <= n; i++) {
        if (!visited[i]) {
            comp++;
            dfs(i, adj, visited);
        }
    }

    fout<<comp;
    return 0;
}