import sys
n,m=map(int,input().split())
k=int(input())
a=[int(input()) for i in range(n-1)]
a.sort()
l=0
r=n-3
cnt=0
while l<r:
	while l<r and a[l]+a[r]<=a[n-2]+k:
		l+=1
	if l<r:
		l+=1
		r-=1
		cnt+=1
if cnt>=m:
	print(-1)
	sys.exit(0)
low=0
high=n-2
for i in range(30):
	mid=int((low+high)/2)
	l=0
	r=n-2
	cnt=0
	while l<mid and mid<r:
		while l<mid and a[l]+a[r]<=a[mid]+k:
			l+=1
		if l<mid:
			l+=1
			r-=1
			cnt+=1
	if l<mid:
		r=mid-1
		while l<r:
			while l<r and a[l]+a[r]<=a[mid]+k:
				l+=1
			if l<r:
				l+=1
				r-=1
				cnt+=1
	elif mid<r:
		l=mid+1
		while l<r:
			while l<r and a[l]+a[r]<=a[mid]+k:
				l+=1
			if l<r:
				l+=1
				r-=1
				cnt+=1
	if cnt>=m:
		low=mid
	else:
		high=mid
print(a[high])