import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        int[] nums = new int[n];

        for (int i = 0; i < n; i++) {
            nums[i] = Integer.parseInt(br.readLine());
        }

        Arrays.sort(nums);

        int sum = 0;
        int i = 0;
        while (i < n && nums[i] < 1) {
            if (i + 1 < n && nums[i+1] <= 0) {
                sum += nums[i] * nums[i+1];
                i += 2;
            } else {
                sum += nums[i];
                i++;
            }
        }

        int j = n - 1;
        while (j >= i && nums[j] > 1) {
            if (j - 1 >= i && nums[j-1] > 1) {
                sum += nums[j] * nums[j-1];
                j -= 2;
            } else {
                sum += nums[j];
                j--;
            }
        }

        while (j >= i) {
            sum += nums[j];
            j--;
        }

        System.out.println(sum);
    }
}