Friend


Time Limit: 1000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1994    Accepted Submission(s): 1003


Problem Description


Friend number are defined recursively as follows.
(1) numbers 1 and 2 are friend number;
(2) if a and b are friend numbers, so is ab+a+b;
(3) only the numbers defined in (1) and (2) are friend number.
Now your task is to judge whether an integer is a friend number.


 



Input


There are several lines in input, each line has a nunnegative integer a, 0<=a<=2^30.


 



Output


For the number a on each line of the input, if a is a friend number, output “YES!”, otherwise output “NO!”.


 



Sample Input


3 13121 12131


 



Sample Output


YES! YES! NO!


 



Source


 

解题思路：

​​参考题解​​


#include<stdio.h>
int main()
{
  int n;
  while(scanf("%d",&n)!=EOF)
  {
    if(n==0){
    printf("NO!\n");
    continue;}
    n++;
    while(n)
    {
      if(n%2==0)
         n/=2;
      else
         break;
    }
    while(n)
    {
      if(n%3==0)
         n/=3;
      else
         break;
    }
    if(n==1)
    printf("YES!\n");
    else
    printf("NO!\n");
  }
  return 0;
}