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

using namespace std;

vector<int> adj[100001];
vector<int> visited;
int res = 0;

void dfs(int node) {
    stack<int> s;
    s.push(node);
    while (!s.empty()) {
        int n = s.top();
        s.pop();
        for (int neigh : adj[n]) {
            if (visited[neigh] == -1) {
                s.push(neigh);
                visited[neigh] = 1;
            }
        }
        if (s.size() > 100) {
            break;
        }
    }
    res++;
}

int not_done() {
    for (auto i = 1; i <= visited.size(); i++) {
        if (visited[i] == -1) {
            if (adj[i].size() == 0) {
                visited[i] = 1;
            }
            return 1;
        }
    }
    return 0;
}

int get_first() {
    for (auto i = 1; i <= visited.size(); i++) {
        if (visited[i] == -1) {
            return i;
        }
    }

    return 0;
}

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

    int n, m;
    fin >> n >> m;

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

    while (not_done()) {
        dfs(get_first());
    }
    fout << res;
    return 0;
}