#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, sum = 0, k;
  cin >> n;
  for (int i = 2; i <= n - 1; i++) {
    k = n;
    while (k > 0) {
      sum += k % i;
      k = k / i;
    }
  }
  int p = n - 2;
  for (int i = sum; i >= 1; i--) {
    if (sum % i == 0 && p % i == 0) {
      sum = sum / i;
      p = p / i;
      break;
    }
  }
  cout << sum << "/" << p;
  return 0;
}
