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