Language: C++

#include <iostream>
#include <queue>
#include <map>
#include <list>
#include <vector>
#include <string>
#include <stack>
#include <limits>
#include <climits>
#include <cassert>
#include <fstream>
#include <cstring>
#include <cmath>
#include <bitset>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <cstdio>
#include <ciso646>
#include <set>
#include <array>
#include <unordered_map>

using namespace std;

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)

#define inf 0x3f3f3f3f
#define PB push_back
#define MP make_pair
#define ALL(a) (a).begin(),(a).end()
#define SET(a,c) memset(a,c,sizeof a)
#define CLR(a) memset(a,0,sizeof a)
#define VS vector<string>
#define VI vector<ll>
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define MIN(a,b) (a>b?b:a)
#define MAX(a,b) (a>b?a:b)
#define pi 2*acos(0.0)
#define INFILE() freopen("in0.txt","r",stdin)
#define OUTFILE()freopen("out0.txt","w",stdout)
#define ll long long
#define ull unsigned long long
#define pii pair<ll,ll>
#define pcc pair<char,char>
#define pic pair<ll,char>
#define pci pair<char,ll>
#define eps 1e-14
#define FST first
#define SEC second
#define SETUP cin.tie(0), ios::sync_with_stdio(false), cout << setprecision(15)

namespace {
	struct input_returnner {
		ll N; input_returnner(ll N_ = 0) :N(N_) {}
		template<typename T> operator vector<T>() const { vector<T> res(N); for (auto &a : res) cin >> a; return std::move(res); }
		template<typename T> operator T() const { T res; cin >> res; return res; }
		template<typename T> T operator - (T right) { return T(input_returnner()) - right; }
		template<typename T> T operator + (T right) { return T(input_returnner()) + right; }
		template<typename T> T operator * (T right) { return T(input_returnner()) * right; }
		template<typename T> T operator / (T right) { return T(input_returnner()) / right; }
		template<typename T> T operator << (T right) { return T(input_returnner()) << right; }
		template<typename T> T operator >> (T right) { return T(input_returnner()) >> right; }
	};
	template<typename T> input_returnner in() { return in<T>(); }
	input_returnner in() { return input_returnner(); }
	input_returnner in(ll N) { return std::move(input_returnner(N)); }
}

const ll MOD = 1e9 + 7;

struct ModInt {
	ll v = 0;
	ModInt() {}
	template<class T> ModInt(const T& right) {
		v = right;
		if (v >= 0) v %= MOD;
		else v += ((-v) / MOD + 1)*MOD;
		v %= MOD;
	}
	void operator = (const ModInt& right) { v = right.v; }
	template<class T> void operator = (const T& right) {
		v = right;
		if (v >= 0) v %= MOD;
		else v = v += ((-v) / MOD + 1)*MOD;
		v %= MOD;
	}

	ModInt operator + (const ModInt& right) { return (v + right.v) % MOD; }
	ModInt operator - (const ModInt& right) { return (MOD - (v - right.v)); }
	ModInt operator * (const ModInt& right) { return (v * right.v) % MOD; }
	ModInt operator / (const ModInt& right) { return v / right.v; }

	void operator += (const ModInt& right) { v = (v + right.v) % MOD; }
	void operator -= (const ModInt& right) { v = (MOD - (v - right.v)); }
	void operator *= (const ModInt& right) { v = (v* right.v) % MOD; }
	void operator /= (const ModInt& right) { v = v / right.v; }

	bool operator == (const ModInt& right) { return v == right.v; }
};

ostream& operator << (ostream& os, const ModInt& value) {
	os << value.v;
	return os;
}

void solve();
/// ---template---

signed main(void) {
	SETUP;
	solve();
	return 0;
}

#define int long long

int getA(int w,int h, int x){
	vector<int> a(3);
	int y = h / 2;
	a[0] = h*x;
	a[1] = y*(w - x);
	a[2] = (h - y)*(w - x);
	return max(ALL(a)) - min(ALL(a));
}

int f(int w, int h) {
	int res = 1e10+1;
	if (h >= 3 and h % 3 != 0) res = w*(h / 3);
	int H = h / 2;
	double x = H*w / double(h + H);
	res = min(abs(H*(w - int(ceil(x))) - int(ceil(x))*h), res);
	H = ceil(h / 2.0);
	x = H*w / (h + H);
	res = min(abs(H*(w - int(x)) - int(x)*h), res);
	return res;
}

void solve() {
	int w, h; cin >> w >> h;
	cout << min(f(w, h), f(h, w)) << endl;
}

Compiler output:
a.cc: In function 'long long int f(long long int, long long int)':
a.cc:119:13: error: expected primary-expression before 'long'
  119 | #define int long long
      |             ^~~~
a.cc:135:30: note: in expansion of macro 'int'
  135 |         res = min(abs(H*(w - int(ceil(x))) - int(ceil(x))*h), res);
      |                              ^~~
a.cc:135:29: error: expected ')' before 'long'
  135 |         res = min(abs(H*(w - int(ceil(x))) - int(ceil(x))*h), res);
      |                         ~   ^
      |                             )
a.cc:119:13: error: expected primary-expression before 'long'
  119 | #define int long long
      |             ^~~~
a.cc:138:30: note: in expansion of macro 'int'
  138 |         res = min(abs(H*(w - int(x)) - int(x)*h), res);
      |                              ^~~
a.cc:138:29: error: expected ')' before 'long'
  138 |         res = min(abs(H*(w - int(x)) - int(x)*h), res);
      |                         ~   ^
      |                             )