#line 2 "/home/defineprogram/Desktop/Library/template/template.cpp"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for (int i = 0; i < n; i++)
#define REP(i, n) for (int i = 1; i < n; i++)
#define rev(i, n) for (int i = n - 1; i >= 0; i--)
#define REV(i, n) for (int i = n - 1; i > 0; i--)
#define all(v) v.begin(), v.end()
#define PL pair<ll, ll>
#define PI pair<int,int>
#define len(s) (int)s.size()

template <class T, class U>
inline bool chmin(T &a, U b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T, class U>
inline bool chmax(T &a, U b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
constexpr ll inf = 3e18;
#line 3 "/home/defineprogram/Desktop/Library/structure/UnionFind.cpp"

class UnionFind {
    int N;
    vector<int> par, siz;

   public:
    int find(int x) {
        assert(x < N);
        return (par[x] == x ? x : par[x] = find(par[x]));
    }
    void merge(int x, int y) {
        assert(x < N && y < N);
        x = find(x);
        y = find(y);
        if (x == y) return;
        if (siz[x] > siz[y]) swap(x, y);
        par[x] = y;
        siz[y] += siz[x];
    }
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    int size(int x) {
        return siz[find(x)];
    }
    UnionFind(int N) : N(N), siz(N, 1), par(N) {
        iota(all(par), 0);
    }
};

/*
@brief Union Find
@docs docs/UnionFind.md
*/
#line 3 "main.cpp"

int N,M;
int pre[1<<18];
int main() {
    cin.tie(0); ios::sync_with_stdio(false);
    cin>>N>>M;
    memset(pre,-1,sizeof(pre));
    UnionFind uf(M);
    rep(i,N){
        int a,b;cin>>a>>b;a--;b--;
        if(pre[b]!=-1){
            uf.merge(a,pre[b]);
        }
        pre[b]=a;
    }
    int ans=0;
    rep(i,M)if(uf.find(i)!=i)ans++;
    cout<<ans<<"\n";
}