#include<bits/stdc++.h>
const int maxn=2e7;
inline const void read(long long &a)
{
	a=0;
	char c=getchar();
	while(c<'0'||c>'9')c=getchar();
	while(c>='0'&&c<='9')
	{
		a=(a<<1)+(a<<3)+c-'0';
		c=getchar();
	}
}
inline const void write(long long a)
{
	if(a>9)write(a/10);
	putchar(a%10+'0');
}
long long n,ans=0,sqrtn;
long long f[maxn];
int main()
{
	//freopen("a.in","r",stdin);
	//freopen("a.out","w",stdout);
	memset(f,0,sizeof(f));
	read(n);sqrtn=sqrt(n);
	for(int i=1;i<=sqrtn;i++)
	{
		f[i*i]--;
		for(int j=i;j*i<=n;j++)f[i*j]+=2;
	}
	for(int i=1;i<=n;i++)ans+=n/i*f[i];
	write(ans);
	return 0;
}