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)

int main(int argc, const char * argv[]) {
    int N,K,X,Y;
    scanf("%d",&N);
    scanf("%d",&K);
    scanf("%d",&X);
    scanf("%d",&Y);
    
    int ans=0;
    if(N>K){
    for(int j=0;j<(N-K);j++){
            ans = ans+Y;
        }
    
    
    for(int i=0;i<K;i++){
        ans = ans+X;
    }
    }
    
    else if(N<K){
        for(int i=0;i<N;i++){
            ans = ans+X;
        }
        
    }
    
    
    printf("%d\n",ans);
    return 0;
}