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,s,i;
    scanf("%d %d %d %d",&N,&K,&X,&Y);
    s=K*X+(N-K)*Y;
   printf("%d\n",s);
    printf("The accommodation fee is as follows:\n");
    for (i=1;i<=N;i++){
        if(i<=K){
                if (i==1){
                printf("%d yen for the %d-st night\n",X,i);
                }
                else if(i==2){
                   printf("%d yen for the %d-nd night\n",X,i);
                }
                else if(i==3){
                   printf("%d yen for the %d-rd night\n",X,i);
                }
                else {
                   printf("%d yen for the %d-th night\n",X,i);
                }
        }
        else if(i>K){
          if (i==1){
               printf("%d yen for the %d-st night\n",Y,i);
                }
                else if(i==2){
                   printf("%d yen for the %d-nd night\n",Y,i);
                }
                else if(i==3){
                   printf("%d yen for the %d-rd night\n",Y,i);
                }
                else {
                   printf("%d yen for the %d-th night\n",Y,i);
                }
        }

    }
printf("thus, the total is %d yen.\n",s);


}