#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  while (b != 0) {
    int newa = b;
    int newb = a % b;
    a = newa;
    b = newb;
  }
  return a;
}
int main() {
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  int s = a * b;
  int p, q;
  if (c * b - a * d >= 0) {
    p = c * b - a * d;
    q = c * b;
  } else {
    p = a * d - c * b;
    q = a * d;
  }
  cout << p / gcd(p, q) << '/' << q / gcd(p, q) << endl;
  return 0;
}
