题解 | 墙壁划线

#include <bits/stdc++.h>
using namespace std;
using LL = long long;
int main() {
    LL a, b, x, y;
    cin >> a >> b >> x >> y;
    LL ans = 0;
    auto g = gcd(x, y);
    x /= g;
    y /= g;
    if (a == b) {
        ans = a + 1 + b + 1;
        if (a % 2 == 0 || b % 2 == 0) ans--;
    } else {
        ans = (a + 1) * 2 + (b + 1) * 2 - 2 * (gcd(a, b) + 1);
        if (a % 2 == 0 || b % 2 == 0) ans--;
    }
    cout << ans << endl;
}