#include #include #include #include #include using namespace std; typedef long long ll; int main() { int n, m, x, y; cin >> n >> m >> x >> y; int p1 = 0, p2 = 0; for(int i = 0; i <= x; i++) { for(int j = 0; j <= x; j++) { if(i + j <= y) { p1 = i; p2 = j; } } } int sum1 = 0; for(int i = 0; i < n; i++) { for(int j = 0; j < m; j++) { if(i % 2 == 0 and j % 2 == 0) { sum1 += p1; } else if(i % 2 == 0 and j % 2 == 1) { sum1 += p2; } else if(i % 2 == 1 and j % 2 == 0) { sum1 += p2; } else { sum1 += p1; } } } int sum2 = 0; for(int i = 0; i < n; i++) { for(int j = 0; j < m; j++) { if(i % 2 == 0 and j % 2 == 0) { sum2 += p2; } else if(i % 2 == 0 and j % 2 == 1) { sum2 += p1; } else if(i % 2 == 1 and j % 2 == 0) { sum2 += p1; } else { sum2 += p2; } } } cout << max(sum1, sum2) << endl; return 0; } // 2222222222 // 22222222222