def kadomatsu original,array
    tmp = [original[array[0]],original[array[1]],original[array[2]]]
    if tmp.minmax == [tmp[0],tmp[2]].sort
        return false
    else
        return true
    end
end
    
n = gets.to_i 
k = gets.split.map(&:to_i)
range = [*0..n-1]
kado = range.combination(3).to_a.select{|a|kadomatsu(k,a)}
if kado.empty?
    puts -1
    exit
end
kado.each{|v|
    if ((range - v).combination(3).to_a.select{|a|kadomatsu(k,a)}.inject(&:|).to_a.size / 3) % 2 == 0
        puts v.join(' ')
        exit
    end
    }
puts -1