#include <stdio.h>

int x[1000010],n,i,j;
long long s;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);

    scanf("%d",&n);
    for(i=2; i<=n; ++i)
    {
        if(x[i]==0)
        {
			s+=i-1;

			for(j=i+i; j<=n; j+=i)
			{
				if(x[j]==0)
					x[j]=j-(j/i);
				else
					x[j]=x[j]-x[j]/i;
			}
		}
		else
			s += x[i];
    }
    printf("%lld",2*s+1);
    return 0;
}