#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) { return b != 0 ? gcd(b, a % b) : a; }
int main() {
  int a;
  cin >> a;
  int ans = 0;
  int i;
  for (i = 2; i < a; i++) {
    int t = a;
    int res = 0;
    int j = i;
    while (t > 0) {
      res += t % j;
      t /= j;
    }
    ans += res;
  }
  int g = gcd(ans, a - 2);
  printf("%d/%d\n", ans / g, (a - 2) / g);
  return 0;
}
