#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(int)(n);i++)

int totient(int x){
	int ret = x;
	for(int p=2;p*p<=x;p++){
		if(x%p==0){
			ret -= ret/p;
			while(x%p==0) x/=p;
		}
	}
	if(x!=1) ret -= ret/x;
	return ret;
}

int main(){
	ll n;
	cin>>n;
	ll ans=0;
	ans+=n*(n-1)/2;
	for(int i=2;i<=n;i++){
		ans-=totient(i);
	}
	for(int i=2;i<=n;i++){
		ans-=n/i-1;
	}
	cout<<ans<<endl;
}