n,m=gets.split.map &:to_i
x=gets.to_i
a=(1...n).map{gets.to_i}.sort.reverse
pos=a.bsearch_index{|y|
j=n-2
(0...n-1).count{|i|
j-=1while i<j&&x+y>=a[i]+a[j]
i>=j ?false:j-=1}>=m}||n-1
p pos>0?a[pos-1]:-1