//尤拉函式打表
#include<iostream>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iomanip>
#include<assert.h>
#include<vector>
#include<list>
#include<map>
#include<set>
#include<sstream>
#include<stack>
#include<queue>
#include<string>
#include<bitset>
#include<algorithm>
#pragma warning(disable:4996)
#define me(s)  memset(s,0,sizeof(s))
#define _for(i,a,b) for(int i=(a);i<(b);++i)
#define _rep(i,a,b) for(int i=(a);i<=(b);++i)
using namespace std;
typedef pair <int, int> pii;
typedef long long ll;
typedef unsigned long long ull;
const int inf = 0x3f3f3f3f;
const int dr[] = { 0, -1, 0, 1, -1, -1, 1, 1 };
const int dc[] = { -1, 0, 1, 0, -1, 1, -1, 1 };
const int MOD = 1e9 + 7;
const double pi = acos(-1.0);
const double eps = 1e-15;
const int maxn = 50000;
int phi[maxn + 1], phi_psum[maxn + 1];

void phi_table(int n) {
	phi[1] = 0;
	for (int i = 2; i <= n; i++) if (phi[i] == 0)
		for (int j = i; j <= n; j += i) {
			if (phi[j] == 0) phi[j] = j;
			phi[j] = phi[j] / i * (i - 1);
		}
}

int main() {
	int n;
	phi_table(maxn);
	phi_psum[0] = 0;
	for (int i = 1; i <= maxn; i++)
		phi_psum[i] = phi_psum[i - 1] + phi[i];
	while (scanf("%d", &n) == 1 && n)
		printf("%d\n", 2 * phi_psum[n] + 1);
	return 0;
}