content: // kangaroo 2 is always starting ahead of kangaroo 1
  // so kangaroo 1 must be faster than kangaroo 2
  // if they have to land at same spot after same number of jumps
  // 
  // now because kangaroo 1 must be faster
  // if kangaroo 1 passes kangaroo 2 without meeting at same spot
  // they langaroo 2 can never catch up to kangaroo 1
  // so they will never meet in this case also
  
  import java.io.*;   //importing io library to use BufferedReader and InputStreamReader
  
  public class solution
  {
      public static void main(String[] args) throws IOException
      {
          BufferedReader reader =new BufferedReader(new InputStreamReader(System.in));  //preparing input stream
          String[] param;
          param = reader.readLine().split("\\s");   //taking space separated input into array
          int int_para[] = new int[4];
          for (int i=0;i<4;i++)
          {
              int_para[i] = Integer.parseInt(param[i]);   //converting string elements to integers
          }
  
          //assigning to respective variables
          int x1 = int_para[0];
          int v1 = int_para[1];
          int x2 = int_para[2];
          int v2 = int_para[3];
          
          if(v1 <= v2)    //if kangaroo 1 speed is slower than or eual to speed of kangaroo 2 then they will never meet
          {
              System.out.println("NO");
          }
          else
          {
              while(x1 <= x2)
              {
                  if(x1 == x2)    //checking for same position
                  {
                      System.out.println("YES");
                      break;
                  }
  
                  //jumps added
                  x1 = x1 + v1;
                  x2 = x2 + v2;
                  
                  if(x1 > x2)   //if kangaroo 1 is ahead of kangaroo 2, then they will never meet
                  {
                      System.out.println("NO");
                  }
              }
          }
      }
  }