#include <cstdio>
FILE *f = fopen("fractii.in","r");
FILE *g = fopen("fractii.out","w");

int n,phi[1000001];

void citire(){
	
	fscanf(f,"%d",&n);
}

long long Phi(int n){

	int i,j;
	long long sol=0;
	for(i=1;i<=n;i++)
		phi[i]=i-1;
	for(i=2;i<=n;i++){
		
		for(j=2*i;j<=n;j+=i)
			phi[j]-=phi[i];
		sol+=phi[i];
	}
	return 2*sol+1;
}

int main(){
	
	citire();
	fprintf(g,"%lld",Phi(n));
	return 0;
}