#include <bits/stdc++.h>

template<class T>
void print(const T &t) { std::cout << t << '\n'; }

template<class Head, class... Tail>
void print(const Head &head, const Tail &... tail) {
    std::cout << head << ' ';
    print(tail...);
}

template<typename T>
using v = std::vector<T>;
using ll = long long;
using std::cin;

struct UnionFind {
    v<int> parent, rank, count;

    explicit UnionFind(int n) :
            parent(n, -1), rank(n, 1), count(n, 1) {
    }

    int get_root(int n) {
        if (parent[n] == -1) {
            return n;
        } else {
            return parent[n] = get_root(parent[n]);
        }
    }

    bool is_same(int i, int j) {
        return get_root(i) == get_root(j);
    }

    void merge(int i, int j) {
        i = get_root(i);
        j = get_root(j);
        if (i == j) {
            return;
        }
        if (rank[i] < rank[j]) {
            std::swap(i, j);
        }
        parent[j] = i;
        rank[i] = std::max(rank[i], rank[j] + 1);
        count[i] += count[j];
    }
};

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);

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

    v<int> col(n, -1);
    UnionFind uf(m);

    for (int i = 0; i < n; ++i) {
        int b, c;
        cin >> b >> c;
        b--;
        c--;
        if (col[c] != -1) {
            uf.merge(b, col[c]);
        }
        col[c] = b;
    }

    int ans = 0;
    for (auto &i: uf.count) {
        ans += i - 1;
    }
    print(ans);
}