#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  if (a == 0 || b == 0)
    return 0;
  else if (a == b)
    return a;
  else if (a > b)
    return gcd(a - b, b);
  else
    return gcd(a, b - a);
}
int main() {
  int a;
  cin >> a;
  int x = a, sum = 0;
  for (int b = 2; b < a; b++) {
    x = a;
    while (x != 0) {
      sum += x % b;
      x /= b;
    }
  }
  int denominator = a - 2;
  int mygcd = gcd(sum, a - 2);
  sum /= mygcd;
  denominator /= mygcd;
  cout << sum << '/' << denominator << endl;
  return 0;
}
