N, K, P = map(int, input().split())
A = sorted(list(map(int, input().split())))
B = sorted(list(map(int, input().split())))

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