#include <bits/stdc++.h>
using namespace std;
long long n;
long long t, w, b;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
long long lcm(long long a, long long b) { return (a * b) / gcd(a, b); }
int main() {
  scanf("%I64d %I64d %I64d", &t, &w, &b);
  if (w < b) {
    swap(w, b);
  }
  long long l = w / gcd(w, b);
  double d = log10((double)l) + log10((double)b);
  l *= b;
  if ((int)ceil(d) > 18) {
    l = t + 1;
  }
  if (w == b) {
    printf("1/1\n");
    return 0;
  }
  long long num = t / l;
  long long add = min(w, b) - 1;
  if (add >= t) {
    add = t;
  }
  long long res = num + add;
  if (num) {
    res += (num - 1) * add;
  }
  long long last_meet = num * l;
  if (last_meet) res += min(t, last_meet + min(w, b) - 1) - last_meet;
  long long g = gcd(res, t);
  res /= g;
  t /= g;
  printf("%I64d/%I64d\n", res, t);
  return 0;
}
