Problem A
Sumsets

Given $S$, a set of integers, find the largest $d$ such that $a+b+c=d$ where $a,b,c$ and $d$ are distinct elements of $S$.

Input

The input starts with an integer $1\le N\le 4000$, the number of elements in $S$. It is followed by $N$ lines containing the elements of $s$, one per line. Each element of $S$ is a distinct integer between $-536870912$ and $+536870911$, inclusive.

Output

Output a single line containing the maximum $d$ as described in the statement. If no such $d$ exists, output a single line containing no solution.

5
2
3
5
7
12

12

5
2
16
64
256
1024

no solution