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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)



import java.util.Scanner;


public class Main {
    
    public static void main(String[] args) {

        int n, k, x, y, total1 = 0, total2 = 0, total;

        Scanner input = new Scanner(System.in);

       // System.out.print("Total Night: ");

        n = input.nextInt();

        //System.out.print("First Night: ");

        k = input.nextInt();

        //System.out.print("X = ");

        x = input.nextInt();

        //System.out.print("Y = ");

        y = input.nextInt();

        if ((n >= 1 && n <= 10000) && (k >= 1 && k <= 10000)) {

            if ((x >= 1 && x <= 10000) && (y >= 1 && y <= 10000)) {

                for (int i = 1; i <= k; i++) {

                    total1 = total1 + x;
                }

                for (int i = 1; i <= n - k; i++) {

                    total2 = total2 + y;
                }
            }
        }


        total = total1 + total2;

        System.out.println(total);
    }
    
}