Climbing Worm

描述
An inch worm is at the bottom of a well n inches deep. It has enough energy to climb u inches every minute, but then has to rest a minute before climbing again. During the rest, it slips down d inches. The process of climbing and resting then repeats. How long before the worm climbs out of the well? We'll always count a portion of a minute as a whole minute and if the worm just reaches the top of the well at the end of its climbing, we'll assume the worm makes it out.
输入
There will be multiple problem instances. Each line will contain 3 positive integers n, u and d. These give the values mentioned in the paragraph above. Furthermore, you may assume d < u and n < 100. A value of n = 0 indicates end of output.
输出
Each input instance should generate a single integer on a line, indicating the number of minutes it takes for the worm to climb out of the well.
样例
样例输入 #1
10 2 1
20 3 1
0 0 0
样例输出 #1
17
19
来源
East Central North America 2002
HDOJ-1049
题目来源:HDOJ-1049
时间限制:1000 MS
内存限制:32768 KB
Java 类名:Main
64 位整数占位符:%I64d