#include <stdio.h>

int main () {
   int a, b, c, d;
   scanf("%d%d%d%d", &a, &b, &c, &d);
   int flag = 1;
   while (1) {
       if (a <= 0) {
           printf("No");
           break;
       }
       if(c <= 0) {
          printf("Yes");
          break;
       }
       if(flag == 0) {
          a -= d;
          flag = 1;
       }
       else if(flag == 1) {
           c -= b;
           flag = 0;
       }      
   }
   printf("\n");
   return 0;
}
