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

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

const int maxn = 4e5 + 5;
vector<int> g[maxn];

int vis[maxn];
int id;
void dfs(int u) {
    vis[u] = id;
    for (int v : g[u])
        if (!vis[v])
            dfs(v);
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < n; i++) {
        int b, c;
        cin >> b >> c;
        g[b].push_back(c + m);
        g[c + m].push_back(b);
    }
    for (int i = 1; i <= m; i++) {
        if (!vis[i]) {
            ++id;
            dfs(i);
        }
    }
    cout << m - id << '\n';
}