Language: C++

#pragma region include
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <string>
#include <queue>
#include <stack>
#include <cmath>
#include <set>
#include <cstdio>
#include <tuple>
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
#define MOD (1e9+7)
#define INF (1e9)
#define LLINF (4e18)
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
void input() {}
template<typename... R> void input(int& f, R&... r) { scanf("%d", &f); input(r...); }
template<typename... R> void input(double& f, R&... r) { scanf("%lf", &f); input(r...); }
template<typename... R> void input(ll& f, R&... r) { scanf("%lld", &f); input(r...); }
template<typename... R> void input(char& f, R&... r) { scanf("%c", &f); input(r...); }
template<typename... R> void input(string& f, R&... r) { cin >> f; input(r...); }
template<typename T, typename... R> void input(vector<T>& f, R&... r) { REP(i, f.size())input(f[i]); input(r...); }
#pragma endregion

int main() {
    int N; input(N);
    vector<int> x(N), y(N);
    map<int,int> xmp, ymp;
    set<int> xst, yst;
    REP(i, N) {
        input(x[i], y[i]);
        xmp[x[i]]++;
        ymp[y[i]]++;
    }
    REP(i, N) {
        if (xmp[x[i]] >= 2 && ymp[y[i]] >= 2) {
            xst.insert(x[i]);
            yst.insert(y[i]);
        }
    }
    REP(i, N) {
        if (xst.find(x[i]) != xst.end()) yst.insert(y[i]);
        if (yst.find(y[i]) != yst.end()) xst.insert(x[i]);
    }
    ll ans = 0;
    ans = max(ans, (ll)xst.size() * yst.size() - N);
    cout << ans << endl;
    getchar(); getchar();
}

Compiler output:
a.cc: In function 'int main()':
a.cc:56:14: error: no matching function for call to 'max(ll&, long long unsigned int)'
   56 |     ans = max(ans, (ll)xst.size() * yst.size() - N);
      |           ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:56:14: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'long long unsigned int')
   56 |     ans = max(ans, (ll)xst.size() * yst.size() - N);
      |           ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:4:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:56:14: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   56 |     ans = max(ans, (ll)xst.size() * yst.size() - N);
      |           ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~