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