poj 2407 Relatives（简单欧拉函数）

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 > , y > , z >  such that a = xy and b = xz.

Input

There are several test cases. For each test case, standard input contains a line with n <= ,,,. A line containing  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

 

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<queue>
 #include<algorithm>
 #include<stdlib.h>
 using namespace std;
 #define ll long long
 ll eular(ll n){
     ll ans=;
     for(ll i=;i*i<=n;i++){
         if(n%i==){
             ans*=i-,n/=i;
             while(n%i==){
                 ans*=i;
                 n/=i;
             }
         }
     }
     if(n>) ans*=n-;
     return ans;
 }
 int main()
 {
     ll n;
     while(scanf("%I64d",&n)==){
         if(n==) break;
         ll ans=eular(n);
         printf("%I64d\n",ans);
     }
     return ;
 }