#include <bits/stdc++.h>
using namespace std;
int gcd(int x, int y) {
  if (y == 0) return x;
  return gcd(y, x % y);
}
int main() {
  int i, j, k, n, m;
  scanf("%d", &n);
  m = 0;
  for (i = 2; i < n; i++) {
    k = n;
    while (k) {
      m += k % i;
      k /= i;
    }
  }
  j = gcd(m, n - 2);
  printf("%d/%d\n", m / j, (n - 2) / j);
}
