#include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>
#include <cmath>
#include <fstream>
#include <cstdlib>

using namespace std;

typedef long long lol;

int n;

struct snow
{
    int pred;
    int x;
    int y;
};

snow a[10000];
bool comp[10000];

int find_p(int x)
{
    if (a[x].pred == x)
        return x;
    else
        return a[x].pred = find_p(a[x].pred);
}

void union_p(int x, int y)
{
    int t = rand() % 2;
    if (t == 0)
        swap(x, y);
    a[x].pred = find_p(y);
    return;
}

int main()
{
    scanf("%d", &n);
    for (int i = 0; i<n; i++)
    {
        int x, y;
        scanf("%d%d", &x, &y);
        a[i].pred = i;
        a[i].x = x;
        a[i].y = y;
    }
    for (int i = 0; i<n-1; i++)
        for (int j = i+1; j<n; j++)
        {
            if (a[i].x == a[j].x || a[i].y == a[j].y)
                if (find_p(i) != find_p(j))
                    union_p(i,j);
        }
    int k = 0;
    for (int i = 0; i<n; i++)
        if (comp[find_p(i)] == 0)
        {
            k++;
            comp[find_p(i)] = 1;
        }
    printf("%d", k-1);
    return 0;
}