n,k,p=map(int, input().split())
al=list(map(int, input().split()))
bl=list(map(int, input().split()))
al.sort()
bl.sort()

from bisect import bisect_left, bisect_right
def check_cnt(val):
    res=0
    for a in al:
        cnt1 = bisect_right(bl, val-a)
        # cnt2 = n - bisect_left(bl, p-a)
        cnt2 = n - bisect_right(bl, p-a-1)
        cnt3 = n - bisect_right(bl, val+p-a)
        res+=(cnt1+cnt2-cnt3)
    return res

ok, ng = 0, p
ok, ng = p-1, -1
while abs(ok-ng) > 1:
    mid = (ok+ng)//2
    res = True
    # ...
    cnt=check_cnt(mid)
    # print('---',mid,cnt)
    if cnt>=k: ok = mid
    else: ng = mid
print(ok)