#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long inv2 = 500000004;
void square(long long& a, long long& b, long long& c) {
  b = (mod * mod + (a * b) % mod + (b * c) % mod) % mod;
  a = (a * a) % mod;
  c = 1;
}
void mult(long long& a, long long& b, long long& c, long long aa, long long bb,
          long long cc) {
  b = (mod * mod + (a * bb) % mod + (b * cc) % mod) % mod;
  a = (a * aa) % mod;
  c = (c * cc);
}
void mod_pow(long long& a, long long& b, long long& c, long long exp) {
  long long ra = 1, rb = 0, rc = 1;
  while (exp) {
    if (exp % 2) {
      mult(ra, rb, rc, a, b, c);
    }
    square(a, b, c);
    exp /= 2;
  }
  a = ra;
  b = rb;
  c = rc;
}
int main() {
  int n;
  scanf("%d", &n);
  long long a = 1, b = 0, c = 1;
  while (n--) {
    long long x;
    scanf("%lld", &x);
    if (x > 1) {
      long long ra = 2, rb = 1, rc = -1;
      mod_pow(a, b, c, x);
      mod_pow(ra, rb, rc, x);
      mult(a, b, c, ra, rb, rc);
      mult(a, b, c, inv2, inv2, -1);
    }
  }
  printf("%lld/%lld\n", b, a);
}
