#include <stdio.h>
int e[1000001];
long long s;

int main()
{
    int n,i,j;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for (i=1;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",2*s+1);
    return 0;
}