source_code: 
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.StringTokenizer;
  
  /**
   *
   * @author Haya
   */
  public class CommentaryBoxes {
  
      public static void main(String[] args) {
          
          FastReader in = new FastReader();
          
          long n = in.nextLong();
          long m = in.nextLong();
          long a = in.nextLong();
          long b = in.nextLong();
          long total = 0;
          
          long val =(n%m);
          if (n%m != 0){
              
              long x = (val)*b;
              long y = (m-val)*a;
              
              total = Math.min(x, y);
          }
          System.out.println(Math.abs(total));
          
      }
  
      public static class FastReader {
  
          BufferedReader br;
          StringTokenizer st;
  
          public FastReader() {
              br = new BufferedReader(new InputStreamReader(System.in));
          }
  
          String next() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          double nextDouble() {
              return Double.parseDouble(next());
          }
  
          String nextLine() {
              String string = "";
              try {
                  string = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return string;
          }
  
      }
  
  }
  