#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int GCD(int a, int b) {
  while (b ^= a ^= b ^= a %= b)
    ;
  return a;
}
int main() {
  int n, a;
  int i, j, ans;
  scanf("%d", &n);
  i = 2;
  ans = 0;
  while (i <= n - 1) {
    a = n;
    while (a) {
      ans += a % i;
      a /= i;
    }
    i++;
  }
  int c = gcd(ans, n - 2);
  printf("%d/%d", ans / c, (n - 2) / c);
  return 0;
}
