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ZOJ Problem Set - 2330
A^B == B^A?

Time Limit: 2 Seconds      Memory Limit: 65536 KB

Solve the equation in the name of this problem.

Input

There are several cases. Each of them has a single real number as the smaller one of a and b in the equation on a separate line. You may assume it's no smaller than 1.1. Proceed until the end of file.

Output

For each case, print the other number on a single line. Keep 5 digits after decimal point. If no such number exists, print -1.

Sample Input

2
10

Sample Output

4.00000
-1


Author: PAN, Minghao
Source: ZOJ 3rd Anniversary Contest
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