C

#include<iostream>
#include<map>
using namespace std;
map<int,int> x;
map<int,int> y;
map<pair<int,int>,int> xy;
int main()
{
int n;
cin>>n;
for(int i=0;i<n;++i)
{
int xx,yy;
scanf("%d%d",&xx,&yy);
++x[xx];
++y[yy];
++xy[make_pair(xx,yy)];
}
long long ans=0;
for(auto i : x) ans+=(long long)i.second*((long long)i.second-1)/2;
for(auto i : y) ans+=(long long)i.second*((long long)i.second-1)/2;
for(auto i : xy) ans-=(long long)i.second*((long long)i.second-1)/2;
printf("%lld",ans);
}