package com.musinsa.point.api;

import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class playground {

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        int N = Integer.parseInt(br.readLine());

        List<Integer> plusList = new ArrayList<>();
        List<Integer> minusList = new ArrayList<>();
        for (int i = 0; i < N; i++) {
            int inputNum = Integer.parseInt(br.readLine());
            if (inputNum > 0) {
                plusList.add(inputNum);
            } else {
                minusList.add(inputNum);
            }
        }

        Collections.sort(plusList, Collections.reverseOrder());
        Collections.sort(minusList);
        int answer = 0;
        // minusList -1
        // plusList 2, 1, 3
        for (int i = 0; i < plusList.size(); i++) {
            System.out.println("i : " + i + " num : " + plusList.get(i));
            Integer num = plusList.get(i);
            // 마지막 것 더하기
            if (i == plusList.size() -1) {
                answer += num;
                break;
            }
            if (num == 1) {
                answer += num;
            } else {
                answer += num * plusList.get(i+1);
            }
        }

        for (int i = 0; i < minusList.size(); i++) {
            System.out.println("i : " + i + " num : " + minusList.get(i));
            answer -= minusList.get(i);
        }

        bw.write(answer + "");	//최대합 BufferedWriter 저장
        bw.flush();		//결과 출력
        bw.close();
        br.close();

    }

}