Language: C++

#ifdef _DEBUG
#include "../../library/library/debug_template.cpp"
#define DMP(...) dump(#__VA_ARGS__, __VA_ARGS__)
#else
#define DMP(...) ((void)0)
#endif

#include <cassert>
#include <cstdio>
#include <cmath>
#include <iostream>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <numeric>
#include <algorithm>

using namespace std;
using lint = long long;
constexpr int MOD = 1000000007, INF = 1010101010;
constexpr lint LINF = 1LL << 60;

struct init {
	init() {
		cin.tie(nullptr); ios::sync_with_stdio(false);
		cout << fixed << setprecision(10);
	}
} init_;

template<class T>
struct Point2D {
	T x, y;
	constexpr Point2D(T x = 0, T y = 0) noexcept : x(x), y(y) {};
	constexpr Point2D(pair<T, T>& p) noexcept : x(p.first), y(p.second) {};
	constexpr bool operator==(const Point2D& rhs) const noexcept { return x == rhs.x && y == rhs.y; }
	constexpr bool operator!=(const Point2D& rhs) const noexcept { return !((*this) == rhs); }
	constexpr bool operator< (const Point2D& rhs) const noexcept { return x < rhs.x || (x == rhs.x && y < rhs.y); }
	constexpr bool operator> (const Point2D& rhs) const noexcept { return rhs < (*this); }
	constexpr bool operator<=(const Point2D& rhs) const noexcept { return !((*this) > rhs); }
	constexpr bool operator>=(const Point2D& rhs) const noexcept { return !((*this) < rhs); }
	constexpr Point2D  operator+ (const Point2D& rhs) const noexcept { return { x + rhs.x, y + rhs.y }; }
	constexpr Point2D  operator- (const Point2D& rhs) const noexcept { return { x - rhs.x, y - rhs.y }; }
	constexpr Point2D  operator* (const T& k) const noexcept { return { k * x, k * y }; }
	constexpr Point2D  operator/ (const T& k) const noexcept { return { x / k, y / k }; }
	constexpr Point2D& operator+=(const Point2D& rhs) noexcept { return ((*this) = (*this) + rhs); }
	constexpr Point2D& operator-=(const Point2D& rhs) noexcept { return ((*this) = (*this) - rhs); }
	constexpr Point2D& operator*=(const T& k) noexcept { return ((*this) = (*this) * k); }
	constexpr Point2D& operator/=(const T& k) noexcept { return ((*this) = (*this) / k); }
	constexpr Point2D  operator- () const noexcept { return { -x, -y }; }
	constexpr T operator* (const Point2D& rhs) const noexcept { return x * rhs.x + y * rhs.y; }
	constexpr Point2D nor() const noexcept { return { y, -x }; }
	constexpr long double hypot() const noexcept { return ::hypotl(x, y); }
	friend istream& operator>>(istream& is, Point2D& p) { return is >> p.x >> p.y; }
	friend ostream& operator<<(ostream& os, const Point2D& p) { return os << p.x << " " << p.y; }
	template<class U> U& operator[](vector<vector<U>>& v) { return v[x][y]; }
};

using pnt = Point2D<lint>;

template<class T>
inline bool chmax(T& a, const T b) { return a < b && (a = b, true); }

int main() {

	int h, w, m;
	cin >> h >> w >> m;

	set<pnt> p;
	map<int, int> row, col;

	for (int i = 0; i < m; i++) {
		int a, b;
		cin >> a >> b;
		a--, b-- ;
		p.emplace(a, b);
		row[a]++;
		col[b]++;
	}

	pair<int, int> mr;
	int a = 0, b = 0;
	for (const auto& [r, nr] : row) {
		if (chmax(a, nr)) mr = make_pair(r, nr);
	}

	lint ans = 1;
	for (const auto& [c, nc] : col) {
		chmax(ans, nc + mr.second - (p.find(pnt(mr.first, c)) != p.end()));
	}

	cout << ans << "\n";

	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:90:22: error: no matching function for call to 'chmax(lint&, int)'
   90 |                 chmax(ans, nc + mr.second - (p.find(pnt(mr.first, c)) != p.end()));
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:63:13: note: candidate: 'template<class T> bool chmax(T&, T)'
   63 | inline bool chmax(T& a, const T b) { return a < b && (a = b, true); }
      |             ^~~~~
a.cc:63:13: note:   template argument deduction/substitution failed:
a.cc:90:22: note:   deduced conflicting types for parameter 'T' ('long long int' and 'int')
   90 |                 chmax(ans, nc + mr.second - (p.find(pnt(mr.first, c)) != p.end()));
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~