import fractions
import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353

n, m = mi()

a = li()
b = li()
c = [0]
for i in range(n):
    c.append(min((b[i] - a[i]), (b[i] + a[i]) % m))
c.append(0)
n = len(c)

dp = [[inf] * 101 for _ in range(n + 1)]
dp[0][0] = 0
for i in range(n - 1):
    for j in range(-50, 51):
        for k in range(-50, 51):
            dp[i + 1][k] = min(dp[i + 1][k], dp[i][j] + abs(c[i] + m * (j - 5) - (c[i + 1] + m * (k - 5))))
print(dp[n - 1][0] // 2)