#include <stack>
#include <cstdio>
#include <list>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <functional>
#include <cstring>
#include <algorithm>
#include <cctype>
#include <string>
#include <map>
#include <cmath>
using namespace std;
#define LL long long
#define ULL unsigned long long
#define SZ(x) (int)x.size()
#define Lowbit(x) ((x) & (-x))
#define MP(a, b) make_pair(a, b)
#define MS(arr, num) memset(arr, num, sizeof(arr))
#define PB push_back
#define X first
#define Y second
#define ROP freopen("input.txt", "r", stdin);
#define MID(a, b) (a + ((b - a) >> 1))
#define LC rt << 1, l, mid
#define RC rt << 1|1, mid + 1, r
#define LRT rt << 1
#define RRT rt << 1|1
#define BitCount(x) __builtin_popcount(x)
#define BitCountll(x) __builtin_popcountll(x)
#define LeftPos(x) 32 - __builtin_clz(x) - 1
#define LeftPosll(x) 64 - __builtin_clzll(x) - 1
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
const double eps = 1e-8;
const int MAXN = 4e6 + 10;
const int MOD = 1000007;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
int cases = 0;
typedef pair<int, int> pii;
typedef vector<int>::iterator viti;
typedef vector<pii>::iterator vitii;
 
int phi[MAXN];
 
void phi_table(int n)
{
    phi[1] = 1;
    for (int i = 2; i <= n; i++)
        if (!phi[i])
            for (int j = i; j <= n; j += i)
            {
                if (!phi[j]) phi[j] = j;
                phi[j] = phi[j] / i * (i-1);
            }
}
 
LL f[MAXN], ans[MAXN];
 
int main()
{
    int n;
    phi_table(MAXN - 1);
    for (int i = 1; i < MAXN; i++)
        for (int j = i * 2; j < MAXN; j += i)
            f[j] += (LL)i * phi[j / i];
    ans[2] = f[2];
    for (int i = 3; i < MAXN; i++) ans[i] = ans[i - 1] + f[i];
    while (scanf("%d", &n), n)
        printf("%lld\n", ans[n]);
    return 0;
}