https://www.acmicpc.net/problem/2217
package boj2217;
import java.io.*;
import java.util.*;
public class Main {
public static void main(String[] args)throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int N = Integer.parseInt(br.readLine());
int [] arr = new int[N];
for(int i = 0; i < N; i++){
arr[i] = Integer.parseInt(br.readLine());
}
Arrays.sort(arr);
int max = Integer.MIN_VALUE;
for(int i = 0; i < N; i++){
max = Math.max(max, arr[i]*(N-i));
}
System.out.println(max);
}
}