import sys
input = sys.stdin.readline

from bisect import bisect,bisect_left

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

A.sort()
B.sort()

OK=P-1
NG=-1

while OK>NG+1:
    mid=(OK+NG)//2

    ANS=0

    for a in A:
        if a+B[0]<=mid:
            x=bisect(B,mid-a)
            y=bisect_left(B,P-a)
            ANS+=x+(N-y)
        elif (a+B[0])%P<=mid:
            x=bisect(B,mid-a+P)
            ANS+=x
        else:
            x=bisect_left(B,P-a)
            y=bisect(B,P+mid-a)
            ANS+=y-x

        #print(a,ANS)

    #print(mid,ANS)

    if ANS>=K:
        OK=mid
    else:
        NG=mid

print(OK)