#include <stdio.h>

long long v[1000002];

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