NYOJ 479 欧拉函数

    水题，不解释。。。题目：

Coprimes

时间限制：500 ms  |  内存限制：4096 KB

难度：1

描述

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).

输入

Input file contains integer N.（ 注意：程序以文件结束符“EOF”结束输入。）

输出

Write answer in output file. 每个数字占一行。

样例输入

9

样例输出

6

ac代码：

#include <iostream>#include <cstdio>#include <cmath>using namespace std;int main(){  int n;  while(~scanf("%d",&n)){    int ans=n;int m=sqrt(n+0.5);for(int i=2;i<=m;++i){  if(n%i==0)  ans=ans-ans/i;  while(n%i==0)  n/=i;}if(n>1)ans=ans-ans/n;printf("%d\n",ans);  }  return 0;}