#include <stdio.h>
#include <string.h>
#include <math.h>
int main(){
	long long n,i,s=1,j,k,phi,nr;
	FILE*f=fopen("fractii.in", "r");
	FILE*g=fopen("fractii.out", "w");
	fscanf(f,"%lld",&n);
	for(i=2;i<=n;i++){
		nr=i;phi=nr;
		for(j=2;j<=sqrt(nr);j++){
			if(nr%j==0)
				phi=(phi*(j-1))/j;
			while(nr%j==0)
				nr/=j;
		}
		if(nr>1)
			phi=(phi*(nr-1))/nr;
                s=s+2*phi;

	}
	fprintf(g,"%lld",s);
	fclose(f);
	fclose(g);
	return 0;

}