#include <bits/stdc++.h>
using namespace std;
std::array<std::array<long long, 2>, 2> mult(
    const std::array<std::array<long long, 2>, 2> &a,
    const std::array<std::array<long long, 2>, 2> &b) {
  std::array<std::array<long long, 2>, 2> c;
  for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 2; j++) {
      c[i][j] = 0;
      for (int k = 0; k < 2; k++) {
        c[i][j] += a[i][k] * b[k][j];
        c[i][j] %= 1000000007;
      }
    }
  }
  return c;
}
std::array<std::array<long long, 2>, 2> matexp(
    std::array<std::array<long long, 2>, 2> a, long long n) {
  std::array<std::array<long long, 2>, 2> res;
  res[0][0] = res[1][1] = 1;
  res[0][1] = res[1][0] = 0;
  while (n) {
    if ((n & 1)) {
      res = mult(res, a);
    }
    a = mult(a, a);
    n >>= 1;
  }
  return res;
}
long long modexp(long long a, long long n) {
  long long res = 1;
  while (n) {
    if ((n & 1)) {
      res *= a;
      res %= 1000000007;
    }
    a *= a;
    a %= 1000000007;
    n >>= 1;
  }
  return res;
}
int main() {
  std::array<std::array<long long, 2>, 2> a;
  a[0][0] = -1;
  a[0][1] = 1;
  a[1][0] = 0;
  a[1][1] = 2;
  int k;
  scanf("%d", &k);
  int mx = 1;
  while (k--) {
    long long x;
    scanf("%lld", &x);
    a = matexp(a, x);
  }
  long long num = (a[0][1]) % 1000000007;
  long long den = (a[1][1]) % 1000000007;
  den *= modexp(2, 1000000007 - 2);
  den %= 1000000007;
  num = (den - num + 1000000007) % 1000000007;
  printf("%lld/%lld\n", num, den);
  return 0;
}
