bzoj 2705: [SDOI2012]Longge的问题

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cmath>
 4 #define ll long long
 5 ll n,m,ans;
 6 ll phi(ll a1)
 7 {
 8     ll sum=a1,m=sqrt(a1);
 9     for(ll i=2;i<=m;i++)
10       if(a1%i==0&&a1)
11         {
12            sum=sum/i*(i-1);
13            for(;a1%i==0;a1/=i); 
14         }
15     if(a1>1)
16       sum=sum/a1*(a1-1);
17     return sum;
18 }
19 int main()
20 {
21     scanf("%lld",&n);
22     m=sqrt(n);
23     for(ll i=1;i<=m;i++)
24       if(n%i==0)
25         {
26             ans+=i*phi(n/i);
27             if(n/i!=i)
28               ans+=n/i*phi(i);
29         }
30     printf("%lld\n",ans);
31     return 0;
32 }