import sys,os,io
input = sys.stdin.readline
#input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
N, K, P = map(int, input().split())
A = sorted(list(map(int, input().split())))
B = sorted(list(map(int, input().split())))
lis = [0]*P
for i in range(N): lis[B[i]] += 1
for i in range(1,P): lis[i] += lis[i-1]

from bisect import *
def check(target):
    cnt = 0
    for i in range(N):
        t = target - A[i]
        if t >= 0: cnt += lis[t]
        cnt += lis[min(P-1, t+P)] - lis[P-1-A[i]]
    return cnt >= K

low,high = -1,P-1
mid = (low+high)//2
while high-low>1:
    if check(mid): high = mid
    else: low = mid
    mid = (low+high)//2
ans = high
print(ans)