code
import java.util.*;
import static java.lang.System.*;
public class Main{
static final int N = 4100000;
/**static long c;*/
static long[] phi = new long[N];
static long[] f = new long[N];
static long[] s = new long[N];
public static void main(String[] args){
Scanner in = new Scanner(System.in);
init();
while(in.hasNext()){
int n = in.nextInt();
if(n == 0) break;
out.println(s[n]);
}
in.close();
}
public static void init(){
for(int i = 0; i < N; ++i){
phi[i] = 0; s[i] = 0;
f[i] = 0;
}
phi[1] = 1;
for(int i = 2; i < N; ++i)
if(phi[i] == 0)
for(int j = i; j < N; j += i){
if(phi[j] == 0) phi[j] = j;
phi[j] = phi[j] / i * (i - 1);
}
for(int i = 1; i < N; ++i)
for(int j = i + i; j < N; j += i)
f[j] += i * phi[j / i];
for(int i = 2; i < N; ++i)
s[i] = s[i - 1] + f[i];
}
}