Problem:
Score : 100 points

Problem Statement

There is a hotel with the following accommodation fee:

X yen (the currency of Japan) per night, for the first K nights

Y yen per night, for the (K+1)-th and subsequent nights

Tak is staying at this hotel for N consecutive nights.
Find his total accommodation fee.

Constraints

1 \leq N, K \leq 10000

1 \leq Y < X \leq 10000

N,\,K,\,X,\,Y are integers.

Input

The input is given from Standard Input in the following format:

N
K
X
Y

Output

Print Tak's total accommodation fee.

Sample Input 1

5
3
10000
9000

Sample Output 1

48000

The accommodation fee is as follows:

10000 yen for the 1-st night

10000 yen for the 2-nd night

10000 yen for the 3-rd night

9000 yen for the 4-th night

9000 yen for the 5-th night

Thus, the total is 48000 yen.

Sample Input 2

2
3
10000
9000

Sample Output 2

20000

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>

int main()
{
	int n,k,x,y;
	int tmp1;   // X円で泊まる日数
	int tmp2;   // Y円で泊まる日数
	int total;  // 合計金額
	
	scanf("%d",&n);
	scanf("%d",&k);
	scanf("%d",&x);
	scanf("%d",&y);
	
	
	
	
	
	/* Y円で泊まるかどうかと日数 */
	if(n > k){ 
		tmp1 = k;
		tmp2 = n-k;
	}else{
		tmp1 = n;
		tmp2 = 0;
	}
	
	total = (tmp1 * x + tmp2 * y);
	
	printf("合計金額は%d円\n",total);
	
	return 0;
}