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

const int MAX_N = 2000020;

map <int, int> mp;

int parent[MAX_N];
int r[MAX_N];

void make_set(int a) {
    parent[a] = a;
    r[a] = 0;
}

int find_set(int a) {
    if (a == parent[a]) {
        return a;
    }

    return parent[a] = find_set(parent[a]);
}

void unite(int a, int b) {
    a = find_set(a);
    b = find_set(b);

    if (r[a] > r[b]) {
        parent[b] = a;
    } else if (r[b] > r[a]) {
        parent[a] = b;
    } else {
        parent[b] = a;
        r[a]++;
    }
}



int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    int united = 0;
    int cur = 0;
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;

        if (mp.find(u) == mp.end()) {
            make_set(cur);
            mp[u] = cur++;
        }

        if (mp.find(v) == mp.end()) {
            make_set(cur);
            mp[v] = cur++;
        }

        u = find_set(mp[u]);
        v = find_set(mp[v]);

        if (u != v) {
            unite(u, v);
            united++;
        }

    }

    cout << n - united << endl;
    return 0;
}