HDU 5310 Souvenir

Problem Description

Today is the 1st anniversary of BestCoder. Soda, the contest manager, wants to buy a souvenir for each contestant. You can buy the souvenir one by one or set by set in the shop. The price for a souvenir is $p$ yuan and the price for a set of souvenirs if $q$ yuan. There's $m$ souvenirs in one set.

There's $n$ contestants in the contest today. Soda wants to know the minimum cost needed to buy a souvenir for each contestant.

Input

There are multiple test cases. The first line of input contains an integer $T$ (1 \le T \le 10^5)(1≤T≤10​5​​), indicating the number of test cases. For each test case:

There's a line containing 4 integers $n,m,p,q$ (1 \le n, m, p, q \le 10^4)(1≤n,m,p,q≤10​4​​).

Output

For each test case, output the minimum cost needed.

Sample Input

2
1 2 2 1
1 2 3 4

Sample Output

1
3


    
    
    
    

     
     
     
     

       Hint 
     
For the first case, Soda can use 1 yuan to buy a set of 2 souvenirs.

     
     
     
     
For the second case, Soda can use 3 yuan to buy a souvenir.
     
     
     
     
 
     
     
     
     
简单题
     
     
     
     
考虑三种情况即可
     
     
     
     

     
     
     
     
#include<cstdio>
#include<cmath>
#include<queue>
#include<vector>
#include<stack>
#include<map>
#include<string>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
typedef long long ll;
const ll maxn = 100005;
int T, n, m, p, q, ans;

int main()
{
    cin >> T;
    while (T--)
    {
        scanf("%d%d%d%d", &n, &m, &p, &q);
        ans = n * p;
        ans = min(ans, n / m * q + n % m * p);
        ans = min(ans, (n + m - 1) / m * q);
        printf("%d\n", ans);
    }
    return 0;
}