#include <bits/stdc++.h>
using namespace std;
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};
long long gcd(long long a, long long b) { return (b == 0 ? a : gcd(b, a % b)); }
int lcm(long long a, long long b) { return (a * (b / gcd(a, b))); }
int main() {
  long long a, b, c, d;
  cin >> a >> b >> c >> d;
  int mul = lcm(c, d);
  a *= mul;
  b *= mul;
  int r = 1;
  while (r * c <= a && r * d <= b) {
    r++;
  }
  c *= (r - 1);
  d *= (r - 1);
  long long ans = gcd(a * b - c * d, a * b);
  cout << (a * b - c * d) / ans << "/" << a * b / ans << endl;
  return 0;
}
