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