/** * @brief Codeforces Round #275 (Div. 2) b * @file b.cpp * @author 面碼 * @created 2014/12/11 18:09 * @edited 2014/12/11 18:09 * @type math binary search * * */#include #include #include #include #include #include #include #include #include using namespace std;#define max(a, b) ((a) > (b) ? (a) : (b))#define min(a, b) ((a) > (b) ? (b) : (a)) #define abs(a) ((a) > 0 ? (a) : (0 - (a)))#define CLR(vec) memset(vec, 0, sizeof(vec))#ifdef DEBUGifstream in;ofstream out;#define CIN in#define COUT out#else#define CIN cin#define COUT cout#endif#define MAXN (2e9 + 10)typedef long long int ll;ll lft, rht, mid;ll cnt1, cnt2, x, y, z;ll i, j, k;ll need1, need2;int main(void){ ios_base::sync_with_stdio(0);#ifdef DEBUG CIN.open("./in", ios::in); COUT.open("./out", ios::out);#endif CIN >> cnt1 >> cnt2 >> x >> y; z = x*y; lft = 2; rht = MAXN; while(lft < rht){ mid = ((rht - lft)/2 + lft); /*set problem*/ i = mid - mid/x; j = mid - mid/y; k = mid - mid/z; k = i + j - k; i -= k; j -= k;#ifdef DEBUG COUT << i << " " << j << " " << k << "\n";#endif if(i < cnt1) k = k - (cnt1 - i); if(j < cnt2) k = k - (cnt2 - j); if(k < 0) lft = mid + 1; /*need more element*/ else rht = mid; /*may get an answer more better*/ } COUT << lft << endl; return 0;}