#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

struct UnionFind {
    UnionFind(int n) : p(n, -1) {}
    int root(int u) {
        return p[u] < 0 ? u : p[u] = root(p[u]);
    }
    int size(int u) {
        return -p[root(u)];
    }
    bool same(int u, int v) {
        return root(u) == root(v);
    }
    void unite(int u, int v) {
        u = root(u);
        v = root(v);
        if (u == v) return;
        if (p[u] > p[v]) swap(u, v);
        p[u] += p[v];
        p[v] = u;
    }
    vector<int> p;
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

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

    UnionFind uf(m);
    vector<int> d(n, -1);
    int r = 0;

    for (int i = 0; i < n; i++) {
        int b, c;
        cin >> b >> c;
        b--; c--;

        int t = d[c];
        d[c] = b;
        if (t < 0) continue;
        if (uf.same(t, b)) continue;
        uf.unite(t, b);
        r++;
    }

    cout << r << endl;

    return 0;
}