import java.io.*;
import java.util.*;

public class MaxPairProduct {
	int numberOfIntegers;
	int biggest;
	int bigger;

	public MaxPairProduct(int size) {
		numberOfIntegers = size;
	}

	public int getCount() {
		return numberOfIntegers;
	}

	public static void main(String[] args) {
		FastScanner s = new FastScanner(System.in);

		int n = s.nextInt();
		MaxPairProduct mpp = new MaxPairProduct(n);
		for (int i = 0; i < n; i++) {
			mpp.newNumber(s.nextInt());
		}

		System.out.println(mpp.getProduct());

	}

	public int getBiggest() {
		return biggest;
	}

	public int getBigger() {
		return bigger;
	}

	public void newNumber(int i) {
		if (i > biggest) {
			bigger = biggest;
			biggest = i;
		} else if (i == biggest) {
			bigger = i;
		} else if (i > bigger) {
			bigger = i;
		}
	}

	public long getProduct() {
		if (numberOfIntegers == 0) {
			return (long) 0;
		} else if (numberOfIntegers == 1) {
			return (long) biggest;
		}
		return (long) biggest * (long) bigger;
	}

	static class FastScanner {
		BufferedReader br;
		StringTokenizer st;

		FastScanner(InputStream stream) {
			try {
				br = new BufferedReader(new InputStreamReader(stream));
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

		String next() {
			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}
	}
}