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