hdu1395 2^x mod n = 1

 1 //Accepted    228 KB    31 ms

 2 #include <cstdio>

 3 #include <cstring>

 4 __int64 n;

 5 void slove()

 6 {

 7     int ans;

 8     __int64 m;

 9     if (n%2==0 || n==1)

10     {

11         printf("2^? mod %I64d = 1\n",n);

12         return ;

13     }

14     m=1;

15     ans=0;

16     int flag=1;

17     while (flag)

18     {

19         ans++;

20         m=2*m%n;

21         if (m==1) flag=0;

22     }

23     printf("2^%d mod %I64d = 1\n",ans,n);

24 }

25 int main()

26 {

27     while (scanf("%I64d",&n)!=EOF)

28     {

29         slove();

30     }

31     return 0;

32 }

hdu1395 2^x mod n = 1