HDU4950:Monster

Teacher Mai has a kingdom. A monster has invaded this kingdom, and Teacher Mai wants to kill it.

Monster initially has h HP. And it will die if HP is less than 1.

Teacher Mai and monster take turns to do their action. In one round, Teacher Mai can attack the monster so that the HP of the monster will be reduced by a. At the end of this round, the HP of monster will be increased by b.

After k consecutive round‘s attack, Teacher Mai must take a rest in this round. However, he can also choose to take a rest in any round.

Output "YES" if Teacher Mai can kill this monster, else output "NO".

There are multiple test cases, terminated by a line "0 0 0 0".

For each test case, the first line contains four integers h,a,b,k(1<=h,a,b,k <=10^9).

For each case, output "Case #k: " first, where k is the case number counting from 1. Then output "YES" if Teacher Mai can kill this monster, else output "NO".

5 3 2 2
0 0 0 0

Case #1: NO

#include <stdio.h>

int main()
{
    __int64 h,a,b,k,cas=1;
    while(~scanf("%I64d%I64d%I64d%I64d",&h,&a,&b,&k),h+a+b+k)
    {
        if(a>=h||(a-b)*k-b>0||(a-b)*(k-1)+a>=h)
            printf("Case #%I64d: YES\n",cas++);
        else
            printf("Case #%I64d: NO\n",cas++);
    }
    return 0;
}