Problem: You are given a positive integer n. Let's build a graph on vertices 1, 2, ..., n in such a way that there is an edge between vertices u and v if and only if <image>. Let d(u, v) be the shortest distance between u and v, or 0 if there is no path between them. Compute the sum of values d(u, v) over all 1 ≤ u < v ≤ n.

The gcd (greatest common divisor) of two positive integers is the maximum positive integer that divides both of the integers.

Input

Single integer n (1 ≤ n ≤ 107).

Output

Print the sum of d(u, v) over all 1 ≤ u < v ≤ n.

Examples

Input

6


Output

8


Input

10


Output

44

Note

All shortest paths in the first example: 

  * <image>
  * <image>
  * <image>
  * <image>
  * <image>
  * <image>



There are no paths between other pairs of vertices.

The total distance is 2 + 1 + 1 + 2 + 1 + 1 = 8.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
const int N = 1e7 + 10;
int pri[N], p[N], phi[N], c[N], s[N];
int n, m, tot, now;
long long s1, s2, s3;
int main() {
  scanf("%d", &n);
  phi[1] = 1;
  for (int i(2); i <= (n); ++i) {
    if (!p[i]) {
      p[i] = pri[++tot] = i;
      phi[i] = i - 1;
    }
    for (int j(1); j <= (tot); ++j) {
      if (i * pri[j] > n) break;
      p[i * pri[j]] = pri[j];
      if (i % pri[j] == 0) {
        phi[i * pri[j]] = phi[i] * pri[j];
        break;
      } else
        phi[i * pri[j]] = phi[i] * (pri[j] - 1);
    }
  }
  for (int i(2); i <= (n); ++i) s1 += 0ll + i - 1 - phi[i];
  for (int i(2); i <= (n); ++i) ++c[p[i]];
  for (int i(2); i <= (n); ++i) s[i] = s[i - 1] + c[i];
  for (int i(2); i <= (n); ++i) s2 += 1ll * c[i] * s[n / i];
  for (int i(2); i <= (n); ++i)
    if (1ll * p[i] * p[i] <= n) --s2;
  s2 /= 2;
  s2 -= s1;
  m = n - 1;
  for (int i(tot); i >= (1); --i) {
    if (pri[i] * 2 > n)
      --m;
    else
      break;
  }
  s3 = 1ll * m * (m - 1) / 2 - s1 - s2;
  printf("%lld\n", s1 + 2 * s2 + 3 * s3);
  return 0;
}