import sys
input = sys.stdin.readline
N, K, P = map(int, input().split())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

bc = [0] * P
for x in b: bc[x] += 1
cs = [0] * (P + 1)
for i in range(P): cs[i + 1] = cs[i] + bc[i]

def check(x):
  c = 0
  for y in a:
    l = (P - y) % P
    r = (P - y + x) % P
    if l <= r: c += cs[r + 1] - cs[l]
    else: c += cs[-1] - cs[l] + cs[r + 1]
  return c >= K

ok = P - 1
ng = -1
while ok - ng > 1:
  m = (ok + ng) // 2
  if check(m): ok = m
  else: ng = m
print(ok)