#include<bits/stdc++.h>
#define int long long
using namespace std;
set<string> s;
int n,a[200005],x[200005],y[200005];
signed main(){
	freopen("Tokitsukazee.in","r",stdin);
	freopen("Tokitsukazee.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin>>n;
	int maxn_x=0,maxn_y=0;
	for(int i=1;i<=n;i++){
		cin>>x[i]>>y[i];
		maxn_x=max(maxn_x,x[i]);
		maxn_y=max(maxn_y,y[i]);
	}
	for(int l=0;l<=maxn_x+1;l++){
		for(int r=0;r<=maxn_x+1;r++){
			for(int i=0;i<=maxn_y+1;i++){
				string st="";
				for(int j=1;j<=n;j++){
					if(x[j]>l&&x[j]<r&&y[j]>i){
						int now=j;
						while(now>0){
							st+=(now%10+'0');
							now/=10;
						}
					}
				}
				if(!st.empty()){
					s.insert(st);
				}
			}
		}
	}
	cout<<s.size();
	return 0;
}