#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long t, w, b, gc = 0, ans = 0, scm = 0;
int main() {
  cin >> t >> w >> b;
  if (w == b) {
    cout << "1/1" << endl;
    return 0;
  }
  if (log(w / gcd(w, b)) + log(b) > log(t) + 1) {
    ans = min(min(b, w) - 1, t);
    gc = gcd(ans, t);
    cout << ans / gc << '/' << t / gc << endl;
    return 0;
  }
  scm = (w / gcd(w, b)) * b;
  if (t < scm) {
    ans = min(t, min(b, w) - 1);
    cout << ans / gcd(ans, t) << '/' << t / gcd(ans, t) << endl;
    return 0;
  }
  t -= scm;
  ans += min(w, b) - 1;
  ans += t / ((b / gcd(b, w)) * w) * min(b, w);
  gc = t % scm;
  ans += min(gc + 1, min(b, w));
  t += scm;
  cerr << ans << " " << gc << endl;
  long long temp = gcd(t, ans);
  cout << ans / temp << "/" << t / temp << endl;
}
