#include<stdio.h>
#define N 1000003
int v[N]={0};
void phi(){
	for(int i=2; i<N;++i)
		v[i]=i;
	for(int i=2; i<N;++i){
		if(v[i]==i){
			for(int j=i; j<N ; j+=i){
				v[j]/=i;
				v[j]*=i-1;
			}
		}
	}
}




int main(){
	freopen("fractii.in", "r", stdin);
	freopen("fractii.out", "w", stdout);
	int n;
	long long s=0;
	scanf("%d", &n);
	phi();
	for(int i=2; i<=n;++i)
		s+=v[i];
	s+=1;
	s+=s-1;
	printf("%lld", s);
	
	return 0;
}