#include <stdio.h>

long long n,i,j,v[1000001],sol=1;

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