#include <bits/stdc++.h>

using namespace std;

#define int long long
#define itn int
#define iont int
#define all(n) (n).begin(), (n).end()
#define pb push_back
#define sz size()
#define mod 1000000007
using vi = vector<int>;
using vvi = vector<vi>;
using vc = vector<char>;
using vcc = vector<vc>;

int xin() {
    int n; cin>>n;
    return n;
}

void ducks(){
    int n;
    cin>>n;
    int fact = 1;
    int fact1 = 1;
    int fact2 = 1;
    for(int i=1; i<=(4*n) - 4; i++){
        fact = fact * i;
        if(i <= (4*n) - 8){
            fact1 = (fact1 * i)%mod;
        }
        if(i <= n){
            fact2 = (fact2 * i)%mod;
        }
    }
    int ans1;
    ans1 = (fact/fact1) + fact2;
    cout<<ans1;

}

void Constantin() {
    int n = xin();
    int prevP = -1;
    int res1 = 0;
    for(int i = 0; i<n; i++) {
        string s; cin>>s;
        for(int j = 0; j<s.sz; j++) {
            char c = s[j];
            if(c == '#') {
                if(i==0) {prevP = j; res1 = 1;}
                else {
                    res1 = (res1 << 1) + (j < prevP);
                }
                prevP = j;
            }
        }
    }
    n = xin();
//    cout<<res1<<endl;
    int res2 = 0;
    for(int i = 0; i<n; i++) {
        string s; cin>>s;
        for(int j = 0; j<s.sz; j++) {
            char c = s[j];
            if(c == '#') {
                if(i==0) {prevP = j; res2 = 1;}
                else {
                    res2 = (res2 << 1) + (j < prevP);
                }
                prevP = j;
            }
        }
    }
//    cout<<res2<<endl;
    int res = res1 + res2;
    vi resV;
    while(res) {
        resV.pb(res %2);
        res /= 2;
    }
    reverse(all(resV));
    int p = 0;
    int pmn = 0, pmx = 0;
    for(int i = 1; i<resV.sz; i++) {
        if(resV[i] == 1) p--;
        else p++;
        pmn = min(pmn, p);
        pmx = max(pmx, p);
    }
//    cout<<res<<endl;
    if(resV.sz == 0) {
        cout<<1<<endl<<'.'<<endl;
        return;
    }
    cout<<resV.sz<<endl;
    int offsetP = -pmn + 1, offsetS = pmx - 1;
    for(int i = 0; i<resV.sz; i++) {
        if(resV[i] == 1)  {
            offsetP--; offsetS++;
        } else {
            offsetP++; offsetS--;
        }
        for(int j = 0; j<offsetP; j++) cout<<'.';
        cout<<'#';
        for(int j = 0; j<offsetS; j++) cout<<'.';
        cout<<endl;
    }
}
/*
 *
3
#..
.#.
..#
3
.#
#.
.#
 */


#define te9 1000000000ll
#define off 2000000005l


void dfsArch(int n, map<int, vi>&g, map<int, bool>& used, int v) {
    used[v] = true;
    for(auto &to : g[v]) {
        if(!used[to]) dfsArch(n, g, used, to);
    }
}
void Archery() {
    itn n=xin();
    map<int, vi>g;
    set<int> s;
    for(int i = 0; i<n; i++) {
        int x=xin(), y = xin() + off;
        g[x].pb(y);
        g[y].pb(x);
        s.insert(x);
        s.insert(y);
    }
    map<int, bool>used;
    int comps = 0;
    for(auto i : s) {
        if(!used[i])  {
            comps++;
//            cout<<i<<' '<<i - off<<endl;
            dfsArch(-1, g, used, i);
        }
    }
    cout<<comps - 1<<endl;
}

signed main() {
    //Snow9();
    // ducks();
    Archery();
}