//a

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define debug(x) cout << #x << " = " << x << "\n";
#define vdebug(a) cout << #a << " = "; for(auto x: a) cout << x << " "; cout << "\n";
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int uid(int a, int b) { return uniform_int_distribution<int>(a, b)(rng); }
ll uld(ll a, ll b) { return uniform_int_distribution<ll>(a, b)(rng); }

void solve(){
    int n;
    cin >> n;
    
    vector<array<int, 2>> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i][1] >> a[i][0];
        a[i][0] = -a[i][0];
        a[i][1] = -a[i][1];
    }
    
    multiset<array<int, 2>> s;
    for (array<int, 2> x : a) s.insert(x);
    
    int ans = 0;
    while (s.size()){
        array<int, 2> cur = *s.begin();
        s.erase(s.find(cur));
        
        auto low = s.lower_bound({cur[1], -INT_MAX});
        while (low != s.end()){
            cur = *low;
            s.erase(s.find(cur));
            low = s.lower_bound({cur[1], -INT_MAX});
        }
        
        ans++;
    }
    
    cout << ans - 1;
}

int main(){
	ios::sync_with_stdio(false);
  	cin.tie(0);
  	cout.tie(0);
    
    solve();
}