import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.nextLine());

		int[] A = new int[N];

		for(int i=0; i<N; i++) {
			String str = sc.nextLine();
			if(str.length() > 1) {
				println("\"assert\"");
				return;
			}
			A[i] = Integer.parseInt(str);
		}

		List<Integer> sum = new ArrayList<>();

		for(int i=0; i<N; i++) {
			for(int j=i; j<N; j++) {
				int result = A[i] + A[j];
				if(!sum.contains(result)) sum.add(result);
			}
		}

		Collections.sort(sum, Comparator.reverseOrder());

		System.out.println(sum.get(2));
	}

	public static void print(Object o) {
		System.out.print(o);
	}

	public static void println(Object o) {
		System.out.println(o);
	}
}