Problem:
Twin Prime

Prime numbers are widely applied for cryptographic and communication technology.
A twin prime is a prime number that differs from another prime number by 2.
For example, (5, 7) and (11, 13) are twin prime pairs.

In this problem, we call the greater number of a twin prime "size of the twin prime."

Your task is to create a program which reads an integer n and prints a twin prime which has the maximum size among twin primes less than or equals to n

You may assume that 5 ≤ n ≤ 10000.

Input

The input is a sequence of datasets. The end of the input is indicated by a line containing one zero. Each dataset is formatted as follows:

n (integer)

Output

For each dataset, print the twin prime p and q (p < q). p and q should be separated by a single space.

Sample Input

12
100
200
300
0

Output for the Sample Input

5 7
71 73
197 199
281 283

Solution in Ruby (judge verdict: Accepted)

def isprime x
    prime = true
    2.upto(Math.sqrt(x)){|y|
        if x % y == 0
            prime = false
            break
        end
    }
    prime
end

primes, twin_primes, max_twin_primes = [], [], []
2.upto(10000){|x| primes << x if isprime x}
prev = primes[0]
primes[1..-1].each{|x|
    twin_primes << [prev, x] if x - prev == 2
    prev = x
}
twin_primes.each{|x, y| max_twin_primes[y] = [x, y]}
5.upto(10000){|i| max_twin_primes[i] = max_twin_primes[i - 1] if max_twin_primes[i].nil?}

while true
    n = gets.to_i
    break if n == 0
    puts max_twin_primes[n].join(" ")
end