#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int main() {
  int n, cn = 0;
  cin >> n;
  for (int i = 2; i < n; i++) {
    int t = n;
    while (t) cn += t % i, t /= i;
  }
  int p = gcd(max(n - 2, cn), min(n - 2, cn));
  cout << cn / p << '/' << (n - 2) / p;
  return 0;
}
