#include <iostream>
 
using std::cin;
using std::cout;
 
int main() {
  int size;
  cin >> size;
  const int INFINITY = 1001;
  int M = INFINITY;
  int min = INFINITY;
  int min_even = INFINITY;
  int next[5];
  cin >> next[0] >> next[1] >> next[2] >> next[3] >> next[4];
  for (int i = 5; i < size; i++) {
    int num;
    cin >> num;
    int mult = num * min;
    if (mult % 2 == 1) {
      mult = num * min_even;
    }
    if (mult < M) {
      M = mult;
    }
    if (next[0] < min) {
      min = next[0];
    }
    if (next[0] % 2 == 0 && next[0] < min_even) {
      min_even = next[0];
    }
    for (int j = 0; j < 4; j++) {
      next[j] = next[j + 1];
    }
    next[4] = num;
  }
  if (M == INFINITY) {
    M = -1;
  }
  cout << M;
 
  return 0;
}

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

MTEKMTIKNDUKNQozCjE3CjIzCjIxCjIwCjE5CjE4CjE3

11
12
45
5
3
17
23
21
20
19
18
17