【反演复习计划】【COGS2431】爱蜜莉雅的求助

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 ll n;
 5 ll calcsum(ll n){
 6     int m=(int)sqrt(n+0.5);
 7     ll cnt=0,ans=0;
 8     for(int i=1;i<=m;i++){
 9         if(n%i==0){
10             ans+=i;if(i*i!=n)ans+=n/i;
11             else break;
12         }
13     }
14     return ans;
15 }
16 ll calcphi(ll n){
17     int m=(int)sqrt(n+0.5);
18     ll ans=n;
19     for(int i=2;i<=m;i++)if(n%i==0){
20         ans=ans/i*(i-1);
21         while(n%i==0)n/=i;
22         if(n==1)break;
23     }
24     if(n>1)ans=ans/n*(n-1);
25     return ans;
26 }
27 int main(){
28     freopen("aimiliyadehelp.in","r",stdin);
29       freopen("aimiliyadehelp.out","w",stdout);
30     cin>>n;
31     cout<<calcsum(n)-calcphi(n)<<endl;
32     return 0;
33 }