package main
import "fmt"

func main() {
 //Enter your code here. Read input from STDIN. Print output to STDOUT
    var result, size int
    fmt.Scanf("%d", &size)
    nums := make([]int, size)
    for i:=0;i<size;i++ {
        fmt.Scanf("%d",&nums[i])
    }
    
    for i:=0; i<size-1; i++ {
        for j:=size; j>i+1; j-- {
            tmp := nums[i:j]
            //fmt.Println(tmp)
            p := product(tmp)
            result = Max(p, result)
        }
    }
    
    fmt.Print(result)
}

func product(x []int) int{
    var product int
    for i := 0; i < len(x); i++ {
        for j := i+1; j < len(x); j++ {
            product = product + x[i]*x[j];
        }
    }
    return product;
}

func Max(x, y int) int {
    if x > y {
        return x
    }
    return y
}