#include<stdio.h>
long f[1000100];
long n,i,j;
long long s;
int main()
{
		freopen("fractii.in","r",stdin);
		freopen("fractii.out","w",stdout);
		scanf("%ld",&n);
		for(i=1;i<=n;++i)
			f[i]=i;
		for(i=2;i<=n;++i)
			if(f[i]==i)
				for(j=2;j<=n;j+=i)
					f[j]=f[j]/i*(i-1);
		for(i=1;i<=n;++i)
			s=s+f[i];
		printf("%lld",2*s-1);
		return 0;
}