POJ 2407 Relatives

Posted 2020-08-17 り挽歌、花开花落的流年

Time Limit: 1000MS		Memory Limit: 65536K
Total 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

7
12
0

Sample Output

6
4

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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