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

def main():
    N,K,P = map(int,input().split()); INF = pow(10,20)
    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)
    #この累積和のメモリが重い
    #sb = [0]*(P+1)
    #for i in range(P):
    #    sb[i+1] = sb[i] + dicb[i]

    #累積和の時値のリストとその位置に対応する累積和をもって二分探索
    LB = list(dicb.keys()); LB.sort()
    sb = [0]
    for i,b in enumerate(LB):
        sb.append(sb[-1] + dicb[b])
    sb += [INF]
    #print(sb)
    #sb[i] - sb[j]: LBのインデックスi以下LBのインデックスj以上 
    
    #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]
                idx1 = bisect.bisect_right(LB,x-i)
                temp = sb[idx1]
                #print(i,"1",temp)
                idx2l = bisect.bisect_left(LB,P-i) #P-iを含まない
                idx2r = bisect.bisect_right(LB,P-1)
                temp += sb[idx2r] - sb[idx2l]
                #print(i,"2",temp)
            else:
                idx2l = bisect.bisect_left(LB,P-i)
                idx2r = bisect.bisect_right(LB,P+x-i)
                temp = sb[idx2r] - sb[idx2l]
                #print(i,"3",temp)
            ret += temp*dica[i]
        #print(x,ret)
        return ret

    #test = 0
    #print(solve(test))
    #exit()

    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()