51nod 1040最大公约数和（欧拉函数）

/*
 * Author:  sweat123
 * Created Time:  2016/6/27 14:01:46
 * File Name: main.cpp
 */
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<cmath>
#include<string>
#include<vector>
#include<cstdio>
#include<time.h>
#include<cstring>
#include<iostream>
#include<algorithm>
#define INF 1<<30
#define MOD 1000000007
#define ll long long
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define pi acos(-1.0)
using namespace std;
const int MAXN = 1000000;
int n;
ll ef(int n) 
{ 
    ll cnt = n; 
    int i; 
    for(i = 2; i * i <= n; i++){ 
        if(n % i == 0) 
        { 
            cnt -= cnt / i;      //   (x-x/p1) *(1-1/p2)*(1-1/p3)*(1-1/p4).....
            while(n % i == 0) 
                n /= i; 
        } 
    }
    if(n > 1) cnt -= cnt / n;
    return cnt; 
} 

int main(){
    while(~scanf("%d",&n)){
        ll ans = 0;
        for(int i = 1; i <= (int)sqrt(n); i++){
            if(n % i == 0){
                ans += ef(n / i) * i;
                if(n / i != i){
                    ans += ef(i) * (n / i);   
                }
            }
        } 
        printf("%lld\n",ans);
    }
    return 0;
}