#include <bits/stdc++.h>

using namespace std;

namespace io {
	const int n = 1e6;
	char c, b[n], *i, *j;
	inline char gc() {
		if (i == j) {
			j = (i = b) + fread(b, 1, n, stdin);
			if (i == j) return EOF;
		} return *i ++;
	}
	#define gc getchar 
	template <typename T = int>
	inline T read() {
		T s = 0; int x = 0;
		while (!isdigit(c = gc())) x |= c == '-';
		for (; isdigit(c); c = gc())
			s = (s << 1) + (s << 3) + (c & 15);
		return x ? - s : s; 
	}
}

using io :: read;

const int N = 5;

int phi[N], s[N];
vector<int> p;

void init(int n) {
	phi[1] = 1;
	for (int i = 2; i <= n; ++ i) {
		if (!phi[i]) {
			phi[i] = i - 1;
			p.emplace_back(i);
		}
		for (int j : p) {
			if (i * j > n) break;
			phi[i * j] = phi[i] * (j - (i % j > 0));
			if (!(i % j)) break;
		}
	}
	s[1] = 3;
	for (int i = 2; i <= n; ++ i)
		s[i] = s[i - 1] + phi[i] * 2;
}

signed main() {
	int n = read(); init(n);
	printf("%d\n", s[n - 1]);
	return 0;
}