#include <iostream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <stack>
#include <utility>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <limits>
#include <sstream>
#include <deque>
#include <bitset>
#include <complex>
#include <functional>
#include <memory>
#include <numeric>

using namespace std;

#define x first
#define y second

int phi[1000007];

void totient(int n) {
	for(int i = 0; i <= n; i++)
		phi[i] = i;

	for(int i = 2; i <= n; i++) {
		if(phi[i] == i)
			for(int j = 2 * i; j <= n; j+=i) {
				phi[j] /= i;
				phi[j] *= (i - 1);
			}
	}
}

int main () {
	ifstream fin("fractii.in");
	ofstream fout("fractii.out");
	int n;
	long long s = 0;
	fin >> n;

	totient(n);

	for(int i = 2; i <= n; i++)
		s+=phi[i];

	fout << 2* s + 1<< endl;

	return 0;
}