My code:

why WA#6

import java.io.*;
import java.util.*;

public class misol1607
{
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int a = in.nextInt();
        int b = in.nextInt();
        int c = in.nextInt();
        int d = in.nextInt();
        int r=c;
        while (a<c)
        {
            if ((a+b)>=c)
            {
                r=c;
                break;
            }
            else
            {
                a=a+b;
            }

            if (a>=(c-d))
            {
                r=a;
                break;
            }
            else
            {
                c=c-d;
            }
        }

        out.println(r);

        out.flush();
   }
}