import bisect

def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    idx = 0
    n = int(data[idx])
    idx += 1
    k = int(data[idx])
    idx += 1
    p = int(data[idx])
    idx += 1
    
    A = list(map(int, data[idx:idx+n]))
    idx += n
    B = list(map(int, data[idx:idx+n]))
    idx += n
    
    B.sort()
    
    low = 0
    high = p - 1
    ans = 0
    
    while low <= high:
        mid = (low + high) // 2
        total = 0
        for a in A:
            L = (p - a) % p
            R = (mid - a) % p
            if L <= R:
                left = bisect.bisect_left(B, L)
                right = bisect.bisect_right(B, R)
                cnt = right - left
            else:
                cnt_high = len(B) - bisect.bisect_left(B, L)
                cnt_low = bisect.bisect_right(B, R)
                cnt = cnt_high + cnt_low
            total += cnt
            if total > k * 2:  # Early exit if possible
                break
        if total >= k:
            ans = mid
            high = mid - 1
        else:
            low = mid + 1
    print(ans)

if __name__ == "__main__":
    main()