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 Python (judge verdict: Accepted)

import bisect as bs
def prime(m):
  N = range(1,m+1, 2)
  N[0] = 2
  n = len(N)
  for i in range(1, n):
    x = N[i]
    if x: N[i+x::x] = [0]*len(N[i+x::x])
  return filter(None, N)

P = prime(10000)
x = []
a = P[0]
for b in P[1:]:
  if b-a==2: x.append(b)
  a=b
while 1:
  n = int(raw_input())
  if n==0: break
  a = x[bs.bisect_right(x, n)-1]
  print a-2, a