POJ1286 Necklace of Beads

 1 /*by SilverN*/
 2 #include<algorithm>
 3 #include<iostream>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 #include<vector>
 8 #define LL long long
 9 using namespace std;
10 int read(){
11     int x=0,f=1;char ch=getchar();
12     while(ch<‘0‘ || ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
13     while(ch>=‘0‘ && ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
14     return x*f;
15 }
16 LL phi(int x){
17     int m=sqrt(x+0.5);
18     LL res=x;
19     for(int i=2;i<=m;i++)
20         if(x%i==0){
21             res=res/i*(i-1);
22             while(x%i==0)x/=i;
23         }
24     if(x>1)res=res/x*(x-1);
25     return res;
26 }
27 int n;
28 int gcd(int a,int b){
29     return (!b)?a:gcd(b,a%b);
30 }
31 LL ksm(LL c,LL k){
32     LL res=1;
33     while(k){
34         if(k&1)res=res*c;
35         c*=c;
36         k>>=1;
37     }
38     return res;
39 }
40 int main(){
41     int i,j;
42     while(1){
43         n=read();
44         if(n==-1)break;
45         if(!n){
46             cout<<0<<endl;
47             continue;
48         }
49         LL ans=0;
50         for(i=1;i<=n;i++){
51             if(n%i==0)ans+=ksm(3,i)*phi(n/i);
52         }
53         if(!(n&1)){
54             ans+=ksm(3,n/2)*n/2;
55             ans+=ksm(3,n/2+1)*n/2;
56         }
57         else ans+=ksm(3,(n+1)/2)*n;
58         ans/=2*n;
59         cout<<ans<<endl;
60     }
61     return 0;
62 }