【分类讨论】bzoj3856 Monster

#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;
}