#include <cstdio>
#include <iostream>
#include <bitset>
#define nmax 1000003
using namespace std;

int n;
int phi[nmax];

int main()
{
    long long sol=0;
    int i,j;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for (i = 1; i <= n; i++) phi[i] = i;
    for(i=2;i<=n;i++)
        if(phi[i]==i)
            for(j=i;j<=n;j+=i) phi[j]=phi[j]/i*(i-1);
    for(i=2;i<=n;i++) sol+=phi[i];
    sol=2*sol+1;
    printf("%lld\n",sol);
    fclose(stdin);
    fclose(stdout);
    return 0;
}