#include <bits/stdc++.h> #define int long long #define pii pair<int,int> #define x first #define y second using namespace std; int n,ans; map <int,int> x,y; vector <pii> v; main(){ cin>>n; for(int k=1;k<=n;k++){ int a,b; cin>>a>>b; x[a]++; y[b]++; v.push_back(make_pair(a,b)); } for(int k=0;k<v.size();k++){ int a=v[k].x,b=v[k].y; int p1=x[a]-1,p2=y[b]-1; ans+=(p1*p2); } cout<<ans; return 0; }

triangle.cpp:10:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main(){
      ^
triangle.cpp: In function 'int main()':
triangle.cpp:19:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 for(int k=0;k<v.size();k++){
             ~^~~~~~~~~