HDU : GCD Again


// @BEGIN_OF_SOURCE_CODE

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cctype>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <sstream>
#include <set>
#include <math.h>
#define pi acos(-1.0)
#define N 1000000
using namespace std;

bool mark [N];
vector <int> primeList;

void sieve ()
{
    memset (mark, true, sizeof (mark));

    mark [0] = mark [1] = false;

    for ( int i = 4; i < N; i += 2 )
        mark [i] = false;

    for ( int i = 3; i * i <= N; i += 2 ) {
        if ( mark [i] ) {
            for ( int j = i * i; j < N; j += 2 * i )
                mark [j] = false;
        }
    }

    primeList.clear ();
    primeList.push_back (2);

    for ( int i = 3; i < N; i += 2 ) {
        if ( mark [i] )
            primeList.push_back (i);
    }

    //printf ("%d\n", primeList.size ());
}

int main ()
{
    sieve ();

    int n;

    while ( scanf ("%d", &n) && n ) {
        int dummy = n;
        int index = 0;
        double countCoPrime = n;

        while ( primeList [index] * primeList [index] <= n && index < primeList.size ()) {
            int primeFactor = 0;
            while ( n % primeList [index] == 0 ) {
                primeFactor = primeList [index];
                n /= primeList [index];
            }

            if ( primeFactor ) {
                countCoPrime *= (1 - (double) 1 / (double)primeFactor);
            }

            index++;
        }

        if ( n > 1 ) {
            countCoPrime *= (1 - (double) 1 / (double)n);
        }

        printf ("%d\n", dummy - (int)countCoPrime - 1);
    }

    return 0;
}

// @END_OF_SOURCE_CODE
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