#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

P op(P a, P b) {
    return max(a, b);
}

P e() {
    return  {-1e18,-1};
}

int main()
{
    int n;
    cin >> n;
    vector<P> vs(n);
    rep(i,n) {
        cin >> vs[i].second >> vs[i].first;
    }
    sort(vs.begin(),vs.end());
    segtree<P, op, e> seg(n);
    rep(i,n) seg.set(i, {vs[i].second,i});
    ll ans = 0;
    vector<ll> y;
    rep(i,n) y.push_back(vs[i].first);
    vector<ll> used(n);
    dbg(y);
    for(int i=n-1;i>=0;i--) {
        if(used[i]) continue;
        ans++;
        int now = i;
        while(true) {
            if(now==-1 || used[now]) break;
            used[now] = 1;
            dbg(vs[now].second);
            int it = upper_bound(y.begin(),y.end(),vs[now].second) - y.begin();
            ll val = seg.prod(0, it).second;
            now = val;
            dbg(val);
        }
    }
    cout << ans-1 << endl;
    return 0;
}