#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define int long long
vector<int> factor(int n) {
  vector<int> ret;
  while(n > 1) {
    bool div = false;
    for(int i = 2; i * i <= n; ++i) {
      if(n % i == 0) {
        ret.push_back(i);
        n /= i;
        div = true;
        break;
      }
    }
    if(div == false) {
      ret.push_back(n);
      break;
    }
  }
  return ret;
}
signed main() {
  int N; cin >> N;
  vector<int> Z(N);
  REP(i,N) cin >> Z[i];
  map<int, int> frac;
  vector<int> f;
  f = factor(Z[0]);
  for(int k : f) frac[k]++;
  f = factor(Z[N-1]);
  for(int k : f) frac[k]--;
  int mul;
  mul = 1;
  for(auto it : frac) {
    if(it.second < 0) {
      REP(i, -it.second) {
        mul *= it.first;
      }
    }
  }
  cout << mul << '/';
  mul = 1;
  for(auto it : frac) {
    if(it.second > 0) {
      REP(i, it.second) {
        mul *= it.first;
      }
    }
  }
  cout << mul << endl;
}