#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

long int largestValue(int size, int* A) 
{
    int max_so_far = INT_MIN, max_ending_here = 0;
 
    for (int i = 0; i < size-1; i++)
    {
        max_ending_here = max_ending_here + A[i]*A[i+1];
        if (max_so_far < max_ending_here)
            max_so_far = max_ending_here;
 
        //if (max_ending_here < 0)
           // max_ending_here = 0;
    }
    return max_so_far;

    // Return the largest value of any of A's nonempty subarrays.
}

int main() {
    int n; 
    scanf("%i", &n);
    int *A = malloc(sizeof(int) * n);
    for (int A_i = 0; A_i < n; A_i++) {
       scanf("%i",&A[A_i]);
    }
    long int result = largestValue(n, A);
    printf("%ld\n", result);
    return 0;
}