http://poj.org/problem?id=2549
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
/**
* Accepted.
*
* @author Administrator
*
*/
public class Main {
private static Set< Long> set = new HashSet< Long>();
private static Map< Long, List< String>> map = new HashMap< Long, List< String>>();
private static Set< Long> sumSet = new HashSet< Long>();
/**
* @param args
*/
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
while (true) {
int n = cin.nextInt();
if (n == 0) {
break;
}
set.clear();
sumSet.clear();
map = new HashMap< Long, List< String>>();
int[] a = new int[n];
for (int i = 0; i < n; i++) {
a[i] = cin.nextInt();
set.add(new Long(a[i]));
}
Arrays.sort(a);
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
if (a[i] != a[j]) {
long temp = a[i];
temp += a[j];
sumSet.add(temp);
}
}
}
for (int i = n - 1; i >= 0; i--) {
for (int j = i - 1; j >= 0; j--) {
if (a[i] == a[j]) {
continue;
}
long v = a[i];
v -= a[j];
if (!sumSet.contains(v)) {
// System.out.println("v=" + v);
continue;
}
List<String> list = map.get(v);
if (list == null) {
list = new ArrayList<String>();
list.add("" + a[i] + " " + a[j]);
} else {
list.add("" + a[i] + " " + a[j]);
}
map.put(v, list);
}
}
int ans = 0;
boolean find = false;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (a[i] == a[j]) {
continue;
}
long sum = a[i];
sum += a[j];
List< String> list = map.get(sum);
// System.out.println("list=" + list);
if (list != null) {
for (String s : list) {
String[] ss = s.split("[ ]+");
int d = Integer.parseInt(ss[0]);
int c = Integer.parseInt(ss[1]);
if (d != a[i] && d != a[j] && c != a[i] && c != a[j]) {
find = true;
ans = Math.max(ans, d);
}
}
}
}
}
if (find) {
System.out.println(ans);
} else {
System.out.println("no solution");
}
}
}
}