#include <bits/stdc++.h>
#define MAXN 1000071
using namespace std;
int PH[MAXN], n;
ifstream fi("fractii.in");
ofstream fo("fractii.out");
int main() {
    fi >> n;
	for(int i = 1; i <= n; ++i)
		PH[i] = i;
	int r = 0;
	for(int i = 2; i <= n; ++i)
	{
		if(PH[i] == i)
			for(int j = i; j <= n; j+=i)
				PH[j] = PH[j] / i * (i-1);
		r += PH[i];
	}
	fo << 2 * r + 1;
    return 0;
}