#include<stdio.h>
long long n,v[1000001],i,j,s;
int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%lld",&n);
    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)
            for(j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
     for(i=2;i<=n;i++)
        s+=v[i];
    printf("%lld",s*2+1);
    return 0;
}