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 C (judge verdict: Time Limit Exceeded)

#include <stdio.h>
int isprime(int n){
    for(int i=2;i*i<=n;i++){
        if(n%i==0)return 0;
    }
    return 1;
}
int main() {
    int x,i,k,p1,p2,ix=0;
    for(k=0;k<10000;k++){
        int sum=0,sumk=0;
        scanf("%d",&x);
        if(x==0)break;
        for(i=1;i<=x;i++){
            p1=isprime(i);
            if(p1==1){
                p2=isprime(i+2);
                if(p2==1){
                    sum=i+i+2;
                }
                if(sum>sumk){
                    sumk=sum;
                    ix=i;
                }
            }
        }
        printf("%d %d",ix,ix+2);
    }
    return 0;
}