【poj 2407 欧拉函数】

Relatives

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 8841		Accepted: 4134

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

 

 

// Project name : 2407 ( Relatives ) 
// File name    : main.cpp
// Author       : Izumu
// Date & Time  : Fri Jul 13 16:13:57 2012


#include <iostream>
#include <stdio.h>
#include <string>
#include <cmath>
#include <algorithm>
using namespace std;

typedef unsigned long long int longint;

longint phi(longint num)
{
    longint sum = 1;
    for (longint i = 2; i <= sqrt(num); i++)
    {
        if(num % i == 0)
        {
            while (num % i == 0)
            {
                sum *= i;
                num /= i;
            }
            sum /= i;
            sum *= (i - 1);
        }
    }

    if (num != 1)
    {
        sum *= (num - 1);
    }

    return sum;
}

int main()
{
    longint number;
    while (cin >> number && number)
    {
        cout << phi(number) << endl;
    }
    return 0;
}

// end 
// ism