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