hdoj1395 （数学水题）2^x mod n = 1

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 12944    Accepted Submission(s): 4018

 

Problem Description

Give a number n, find the minimum x(x>0) that satisfies 2^x mod n = 1.

 

Input

One positive integer on each line, the value of n.

 

Output

If the minimum x exists, print a line with 2^x mod n = 1.

Print 2^? mod n = 1 otherwise.

You should replace x and n with specific numbers.

 

Sample Input

2
5

 

Sample Output

2^? mod 2 = 1
2^4 mod 5 = 1

 #include<stdio.h>
int main()
{
 int n;
 while(scanf("%d",&n)!=EOF)
 {
  int d=0,s=1;
  if(n%2==0||n==1)
  {
   printf("2^? mod %d = 1\n",n);
  }
  else
  {
   while(1)
   {
    s*=2;d++;
    s%=n;
    if(s%n==1)
    {
     printf("2^%d mod %d = 1\n",d,n);
     break;
    }
   }
  }
 }
}