"""

K番目に来る値はX以下か？
NONONONONOYESYESYESYES
          ↑

X以下の値の数を求めてK以上か確かめればよい

"""

import bisect
from sys import stdin
import sys

N,K,P = map(int,stdin.readline().split())

A = list(map(int,stdin.readline().split()))
B = list(map(int,stdin.readline().split()))

for i in range(N):
    A[i] %= P
    B[i] %= P

A.sort()
B.sort()

#print (A,B,file=sys.stderr)

l = -1
r = P-1

while r-l != 1:

    MID = (l+r)//2

    ans = 0

    for i in range(N):
        
        ZR = (P - A[i]) % P
        ZIND = bisect.bisect_left(B,ZR)

        MR = (MID-A[i]) % P
        MIND = bisect.bisect_right(B,MR)

        if ZIND == MIND:
            if (A[0]+B[0]) % P <= MID:
                ans += N
            else:
                ans += 0
        else:
            ans += (MIND-ZIND) % N

    if ans >= K:
        r = MID
    else:
        l = MID

    

print (r)