SGU102 - Coprimes

102. Coprimes

time limit per test: 0.5 sec. 
memory limit per test: 4096 KB

 

For given integer N (1<=N<=10⁴) find amount of positive numbers not greater than N that coprime with N. Let us call two positive integers (say, A and B, for example) coprime if (and only if) their greatest common divisor is 1. (i.e. A and B are coprime iff gcd(A,B) = 1).

 

Input

Input file contains integer N.

 

Output

Write answer in output file.

 

Sample Input

9

Sample Output

6
题解：直接枚举。。。睡觉之前果断怒水一题啊，嘿嘿。WA了一次，木有考虑到 gcd(1,1)=1的情况。。。

View Code

 1 #include<stdio.h>

 2 long gcd(long a,long b)

 3 {

 4     if(b==0) return a;

 5     else

 6     return gcd(b,a%b);

 7 }

 8 int main(void)

 9 {

10     long n,i,ans;

11     ans=0;

12     scanf("%ld",&n);

13     for(i=1;i<=n;i++)

14     if(gcd(i,n)==1)

15     ans++;

16     printf("%ld\n",ans);

17     return 0;

18 }