from collections import defaultdict
import sys 
input = sys.stdin.buffer.readline

def main():
    N,K,P = map(int,input().split())
    A = list(map(int,input().split()))
    B = list(map(int,input().split()))
    dica = defaultdict(int)
    dicb = defaultdict(int)
    for a,b in zip(A,B):
        dica[a%P] += 1
        dicb[b%P] += 1
    #print(dica,dicb)
    sb = [0]*(P+1)
    for i in range(P):
        sb[i+1] = sb[i] + dicb[i]
    #print(sb)
    #和がx以下となるのがk個以上あるか

    def solve(x):
        ret = 0
        for i in dica:
            if i <= x:
                temp = sb[x-i+1] - sb[0]
                temp += sb[P] - sb[P-i]
            else:
                temp = sb[P+x-i+1] - sb[P-i]
            ret += temp*dica[i]
        #print(x,ret)
        return ret

    if solve(0) >= K:
        print(0);exit()

    ok = P
    ng = 0 #これは事前にチェック

    while abs(ok-ng) > 1:
        mid = (ok+ng)//2
        #print(mid)
        if solve(mid) >= K:
            ok = mid
        else:
            ng = mid
    #print(solve(2))
    print(ok)

if __name__ == '__main__':
    main()