import sys
from itertools import accumulate
sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N,K,P = MI()
A = LI()
B = LI()

count = [0]*P
for b in B:
    count[b] += 1
S_count = list(accumulate(count))

ng = -1
ok = P-1
while ng+1 < ok:
    mid = (ng+ok)//2
    c = 0
    for i in range(N):
        a = A[i]
        if mid >= a:
            c += S_count[mid-a]
        c += S_count[min(P-1,P+mid-a)]-S_count[P-a-1]
    if c >= K:
        ok = mid
    else:
        ng = mid

print(ok)