HDU 4983 Goffi and GCD（欧拉函数模板）

LL Eular(LL n)
{
    LL i, ans = 1;

    for (i = 2; i*i <= n; i++)
    {
        if (n % i == 0)
        {
            ans *= i-1;
            n /= i;

            while (n > 0 && n % i == 0)
            {
                n /= i;
                ans *= i;
            }
        }
    }

    if (n > 1) ans *= n-1;

    return ans;
}

#include<stdio.h>
#include<string.h>
#include<queue>
#include<math.h>
#include<stdlib.h>
#include<algorithm>
using namespace std;

const int N=1e6+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;

typedef long long LL;

LL Eular(LL n)
{
    LL i, ans = 1;

    for (i = 2; i*i <= n; i++)
    {
        if (n % i == 0)
        {
            ans *= i-1;
            n /= i;

            while (n > 0 && n % i == 0)
            {
                n /= i;
                ans *= i;
            }
        }
    }

    if (n > 1) ans *= n-1;

    return ans;
}

int main ()
{
    LL n, k, ans, i, num;

    while (scanf("%lld %lld", &n, &k) != EOF)
    {
        ans = num = 0;

        if (k == 2 || n == 1) ans = 1;
        else if (k == 1)
        {
            for (i = 1; i*i <= n; i++)
            {
                if (n % i == 0)
                {
                    if (i*i != n) ans = (ans + Eular(n/i)*Eular(i)*2) % MOD;
                    else ans = ans = (ans + Eular(n/i)*Eular(i)) % MOD;
                }
            }
        }

        printf("%lld\n", ans);
    }

    return 0;
}