nunta- cerinta a

#include <bits/stdc++.h>

using namespace std;

ifstream fin("nunta.in");
ofstream fout("nunta.out");

const int N_MAX = 2e4 + 5;

int n, m, groups;
vector <int> unions[N_MAX], root, sums;

void union_2(vector <int> &a, vector <int> &b) {
    vector <int> *x, *y;
    if (a.size() >= b.size()) {
        x = &a;
        y = &b;
    } else {
        x = &b;
        y = &a;
    }

    int index = root[(*x)[0]];
    for (const auto &i : (*y)) {
        (*x).emplace_back(i);
        root[i] = index;
    }

    (*y).clear();
}

int main() {
    fin >> n >> m;

    root.resize(n + 1);
    for (int i = 1; i <= n; ++i) {
        unions[i].emplace_back(i);
        root[i] = i;
    }

    while (m--) {
        int x, y;
        fin >> x >> y;
        int rx = root[x], ry = root[y];
        if (rx != ry) {
            union_2(unions[rx], unions[ry]);
        }
    }

    for (int i = 1; i <= n; ++i) {
        int size_group = (int) unions[i].size();
        if (size_group > 1) {
            ++groups;
        }
    }

    fout << groups;

    fin.close();
    fout.close();

    return 0;
}