#include<stdio.h>
int main()
{
	int n;
	scanf("%d", &n);
	int i, j;
	long long int a[3];
	char c[3];
	scanf("%c", &c[0]);
	for (i = 0; i < n; i++)
		scanf("%lld%c", &a[i], &c[i]);
	if (c[0] == ' ' || c[1] == ' ' || c[2] == ' ')
	{
		printf("assert\n");
		return 0;
	}
	long long int b[10];
	for (i = 0; i < n; i++)
		for (j = 0; j < n; j++)
			b[n * i + j] = a[i] + a[j];
	for (i = 0; i < n * n - 1; i++)
	{
		if (b[i] < b[i + 1])
		{
			b[i + 1] ^= b[i];
			b[i] ^= b[i + 1];
			b[i + 1] ^= b[i];
			if (i > 0)
				i -= 2;
		}
	}
	i = 2;
	while (b[i] == b[i - 1])
		i++;
	printf("%lld\n", b[i]);
	return 0;
}