object Solution {

    def largestValue(A: Array[Int]): Long =  {
  // Return the largest value of any of A's nonempty subarrays.
  val l = A.toList
  var max = 0
  var i = 0
  while (i < l.length) {
    var j = i+1
    while (j < l.length) {
      if (i-j == 1) {
        if (l(i) > max){
          max = l(i)
        }
      }
      else {
        val value = l.combinations(2).toList.map(x => x(0) * x(1)).sum
        if (value > max)
          max = value
      }
        j=j+1
    }
      i=i+1
  }
  return max
}

    def main(args: Array[String]) {
        val sc = new java.util.Scanner (System.in);
        var n = sc.nextInt();
        var A = new Array[Int](n);
        for(A_i <- 0 to n-1) {
           A(A_i) = sc.nextInt();
        }
        val result = largestValue(A);
        println(result)
    }
}