text: #include <iostream>
  using namespace std;
  
  int main()
  {
      int A, B, C, D;
      cin >> A >> B >> C >> D;
      while(1) {
          C -= B;
          if(C <= 0) {
              cout << "Yes" << endl;
              break;
          }
          A -= D;
          if(A <= 0) {
              cout << "No" << endl;
              break;
          }
      }
  
      return 0;
  }
  