#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
      int t=1;
     __int64 h,a,b,k;
    while(~scanf("%I64d%I64d%I64d%I64d",&h,&a,&b,&k))
    {
        if(h==0&&a==0&&b==0&&k==0)
              break;
         printf("Case #%d: ",t++);

         if(h<=a)
           {

              printf("YES\n");
               continue;
           }
           if(a<=b)
              {
                  printf("NO\n");
                  continue;
              }
        if(h-((a-b)*(k-1)+a)<=0)
           {

              printf("YES\n");
               continue;
           }

         if(h-(a-b)*k+b>=h)
            {
                printf("NO\n");
                continue;
            }
        else
          {

              printf("YES\n");
              continue;
          }
    }
    return 0;
}