#include<cstdio>

using namespace std;

int T=0;

long long h,a,b,k;

int main()

{

	freopen("bzoj3856.in","r",stdin);

    while(1)

	  {

	  	scanf("%lld%lld%lld%lld",&h,&a,&b,&k);

        if (!h&&!a&&!b&&!k) break;

        printf("Case #%d: ",++T);

        if (h <= a) puts("YES");//One Turn Kill;

        else if (a*k > b*(k+1)) puts("YES");//每一轮都能造成伤害;

        else if (a*k-b*(k-1) >= h) puts("YES");//在第k轮或之前干翻对手;

        else puts("NO");

      }

	return 0;

}