#include <bits/stdc++.h>
using namespace std;
long long n;
int main(int argc, char const *argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n;
  long long k, sum = 0, deno = n - 2;
  for (int i = 2; i < n; ++i) {
    k = n;
    while (k > 0) {
      sum += k % i;
      k /= i;
    }
  }
  for (int i = 2; i < n; ++i) {
    while (sum % i == 0 and deno % i == 0) {
      sum /= i;
      deno /= i;
    }
  }
  cout << sum << '/' << deno << endl;
  return 0;
}
