#include <fstream>

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

int main()
{
	int v[100],ie,n,total=1;
	in>>n;
	int i,j,ok,k=1;
	v[0]=2;
	for(i=3;i<=n;i++){
		ok=0;
		for(j=2;j*j<i;j++){
			if(i%j==0){ok=1;
			}
		}
		if(ok==0){v[k]=i;
			k++;
		}
	}
	for(i=2;i<=n;i++){
		ie=i;
		for(j=0;j<k;j++){
			if(v[j]<=i){
				if(i%v[j]==0){
					ie=(ie*(v[j]-1))/v[j];
				}
			}else{
				continue;
			}
		}
		total=total+2*ie;
	}
	out<<total<<endl;
	return 0;
}