import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;
import std.container;

alias sread = () => readln.chomp();
ulong MOD = 1_000_000_007;
ulong INF = 1_000_000_000_000;
ulong MIDDLE = 100_000;
alias Side = Tuple!(long, "from", long, "to");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

void main()
{
    auto n = lread();
    auto a = aryread();
    auto wood = new long[](MIDDLE);
    foreach(e; a)
        wood[e - 1]++;
    
    wood[] /= 2;
    long row, hei;
    foreach_reverse(i, e; wood)
    {
        if(e > 1 && !row && !hei)
        {
            row = hei = i + 1;
            break;
        }
        
        if(e && !row)
            row = i + 1;
        else if(e && !hei)
            hei = i + 1;
    }
    writeln(row * hei);
}
