1 #include <algorithm>
2 #include <iostream>
3 #include <iomanip>
4 #include <cstring>
5 #include <cstdlib>
6 #include <climits>
7 #include <sstream>
8 #include <fstream>
9 #include <cstdio>
10 #include <string>
11 #include <vector>
12 #include <queue>
13 #include <cmath>
14 #include <stack>
15 #include <map>
16 #include <set>
17
18 using namespace std;
19 typedef pair<int,int> II;
20 typedef vector<int> IV;
21 typedef vector<II> IIV;
22 typedef vector<bool> BV;
23 typedef long long i64;
24 typedef unsigned long long u64;
25 typedef unsigned int u32;
26 #define For(t,v,c) for(t::const_iterator v=c.begin(); v!=c.end(); ++v)
27 #define IsComp(n) (_c[n>>6]&(1<<((n>>1)&31)))
28 #define SetComp(n) _c[n>>6]|=(1<<((n>>1)&31))
29 const int MAXP = 46341; //sqrt(2^31)
30 const int SQRP = 216; //sqrt(MAX)
31 int _c[(MAXP>>6)+1];
32 IV primes;
33 void prime_sieve() {
34 for ( int i = 3; i <= SQRP; i += 2 )
35 if ( !IsComp(i) ) for ( int j = i*i; j <= MAXP; j+=i+i ) SetComp(j);
36 primes.push_back ( 2 );
37 for ( int i = 3; i <= MAXP; i += 2 ) if ( !IsComp(i) ) primes.push_back ( i );
38 }
39 int euler_phi ( int n ) {
40 int ans = n;
41 int sn = sqrt ( n );
42 For ( IV, it, primes ) {
43 int prime = *it;
44 if ( prime > sn ) break; if ( n % prime ) continue;
45 for ( ; n%prime == 0; n/= prime );
46 ans /= prime;
47 ans *= (prime-1);
48 sn = sqrt(n);
49 }
50 if ( n > 1 ) ans /= n, ans *= (n-1);
51 return ans;
52 }
53 i64 sum[4000050],phi[4000050],f[4000050];
54 int main()
55 {
56 prime_sieve ( );
57 i64 n,i,j,len,d;
58 for(i=2;i<=4000000;i++)
59 phi[i]=euler_phi(i);
60 memset(f,0,sizeof(f));
61 for(i=1;i<=4000000;i++)
62 {
63 for(j=i;j<=4000000;j+=i)
64 f[j]+=i*phi[j/i];
65 }
66 sum[2]=1;
67 for(i=3;i<=4000000;i++)
68 sum[i]=f[i]+sum[i-1];
69 while(scanf("%lld",&n)!=EOF&&n)
70 {
71 printf("%lld\n",sum[n]);
72 }
73 return 0;
74 }
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