杭电13952^x mod n = 1

2^x mod n = 1

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 14658    Accepted Submission(s): 4527

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

25

 

Sample Output

2^? mod 2 = 12^4 mod 5 = 1

 

Author

MA, Xiao

 

Source

ZOJ Monthly, February 2003

 

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