1
2 /* 交表 _________________________________________________________________________________
3
4 #include <iostream>
5 #include <map>
6 #include <cmath>
7 #include <vector>
8 #include <cstdio>
9 #include <string>
10 #include <cstring>
11 #include <algorithm>
12 using namespace std;
13 #define fir first
14 #define sec second
15 #define pb(x) push_back(x)
16 #define mem(A, X) memset(A, X, sizeof A)
17 #define REP(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
18 #define rep(i,l,u) for(int (i)=(int)(l);(i)>=(int)(u);--(i))
19 #define foreach(e,x) for(__typeof(x.begin()) e=x.begin();e!=x.end();++e)
20 typedef long long LL;
21 typedef unsigned long long ull;
22 typedef pair<long,long> pll;
23
24
25 LL T,n;
26 const int mod=1e9+7;
27 const int maxn=1e5+10;
28
29 const int size=50000;//1-10000的表
30 int phi[size+1];
31 void phi_table() // 1 到 n 的欧拉phi函数值表 ( O( nlg(lgn) ) )
32 {
33 for(int i=2;i<=size;i++)
34 {
35 phi[i]=0;
36 }
37 phi[1]=1;
38 for(int i=2;i<=size;i++)
39 {
40 if(!phi[i])
41 {
42 for(int j=i;j<=size;j+=i)
43 {
44 if(!phi[j]) phi[j]=j;
45 phi[j] = phi[j]/i*(i-1);
46 }
47 }
48 }
49 }
50
51 int main()
52 {
53 freopen("in.txt","r",stdin);
54 phi_table();
55 while(cin>>n&&n)
56 //while(cin>>T)
57 {
58 //REP(kase,1,T) { }
59 LL ans=1;
60 REP(i,2,n)
61 ans+=2*phi[i];
62 cout<<ans<<endl;
63
64 }
65 return 0;
66 }
67
68 /*
69 note :
70 debug :
71 optimize:
72 */
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