POJ 2407 Relatives

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Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 13920 Accepted: 6965

Description

Given n, a positive integer, how many positive integers less than n are relatively prime to n? Two integers a and b are relatively prime if there are no integers x > 1, y > 0, z > 0 such that a = xy and b = xz.

Input

There are several test cases. For each test case, standard input contains a line with n <= 1,000,000,000. A line containing 0 follows the last case.

Output

For each test case there should be single line of output answering the question posed above.

Sample Input

Sample Output

Source

Waterloo local 2002.07.01

 1 #include<cstdio> 2 int euler_phi(int p){ 3     int phi=p; 4     for(int i=2;i*i<=p;i++){ 5         if(!(p%i)){ 6             phi=phi-phi/i; 7             while(!(p%i)) 8                 p/=i; 9         }10     }11     if(p>1)12         phi=phi-phi/p;13     return phi;14 }15 int main(){16     int p;17     while(scanf("%d",&p),p)18         printf("%d\n",euler_phi(p));19     return 0;20 }

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