Expectation Division
Time Limit: 6000/3000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 0 Accepted Submission(s): 0
Special Judge
Problem Description
To be frank with you, this problem is a classic problem of tremendous magnitude which may increase the difficulty of this problem.
We define a type of operation concerning a positive integer n
(n>1)
as to replace it with an integer d
, one of factors of n
(1≤d≤n)
.
You are given a positive integer n
and then we will ask you to determine the expectation number of times to utilize this type of operation if we want to change n
into 1
by operating again and again, assuming each possible d
in each operation has equal possibility to select.
For the sake of calculation, n
and all its distinct prime factors p1,p2,?,pm
will be given, satisfying n
has m
distinct prime factors exactly.
Input
The input contains multiple test cases.
For each test case:
The first line contains two positive integers n
and m
which indicates m
is the number of distinct prime factors of n
, satisfying 2≤n≤1024
.
The second lines contains m
distinct prime numbers p1,p2,?,pm
, satisfying 2≤pi≤106
.
About 2⋅105
test cases in total.
Warm Tips for C/C++: __int128_t is available here but standard solutions of this problem do not use this compiler-dependent data type.
Output
For each test case, output "Case #x
: y
" in one line (without quotes), where x
indicates the case number starting from 1
and y
denotes the expectation number of times to utilize this type of operation of corresponding case. Your answer will be considered correct if its absolute or relative error won‘t exceed 10−9
.
Sample Input
2 1
2
4 1
2
6 2
2 3
8 1
2
10 2
2 5
12 2
2 3
Sample Output
Case #1: 2.0000000000
Case #2: 2.5000000000
Case #3: 2.6666666667
Case #4: 2.8333333333
Case #5: 2.6666666667
Case #6: 3.0333333333