import bisect

n, k, p = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
A.sort()
B.sort()

low = 0
high = p - 1
ans = -1

while low <= high:
    mid = (low + high) // 2
    part1 = 0
    j = n - 1  # B is sorted in ascending order
    for a in A:
        while j >= 0 and (a + B[j]) > mid:
            j -= 1
        part1 += j + 1

    part2 = 0
    for a in A:
        lower = p - a
        upper = mid + p - a
        lower = max(lower, 0)
        upper = min(upper, p - 1)
        if lower > upper:
            continue
        left = bisect.bisect_left(B, lower)
        right = bisect.bisect_right(B, upper)
        part2 += (right - left)

    total = part1 + part2
    if total >= k:
        ans = mid
        high = mid - 1
    else:
        low = mid + 1

print(ans)