#include <bits/stdc++.h>
int n, g, ans;
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int main() {
  scanf("%d", &n);
  ans = 0;
  for (int i = 2; i < n; i++) {
    for (int x = n; x; x /= i) ans += x % i;
  }
  g = gcd(ans, n - 2);
  printf("%d/%d\n", ans / g, (n - 2) / g);
  return 0;
}
