from bisect import bisect_right
from collections import deque
N,S = map(int,input().split())
X = [0]+list(map(int,input().split()))
W = [0]+list(map(int,input().split()))
ind = bisect_right(X,S)
X = X[:ind]+[S]+X[ind:]
W = W[:ind]+[0]+W[ind:]
INFTY = 2*10**15
dp = [[[INFTY for _ in range(2)] for _ in range(N+2)] for _ in range(N+2)]
dp[ind][ind][0] = 0
dp[ind][ind][1] = 0
l = ind
r = ind
A = [0]*(N+2)
for i in range(1,N+2):
    A[i] = A[i-1]+W[i]
que = deque([(l,r)])
visited = set()
visited.add((l,r))
while que:
    l, r = que.popleft()
    if l==1 and r==N+1:continue
    if l>1:
        dp[l-1][r][0] = min(dp[l-1][r][0],dp[l][r][0]+(A[N+1]-(A[r]-A[l-1]))*(X[l]-X[l-1]),dp[l][r][1]+(A[N+1]-(A[r]-A[l-1]))*(X[r]-X[l-1]))
        dp[l-1][r][1] = min(dp[l-1][r][1],dp[l][r][0]+(A[N+1]-(A[r]-A[l-1]))*(X[l]-X[l-1])+(A[N+1]-(A[r]-A[l-1])-W[l-1])*(X[r]-X[l-1]),dp[l][r][1]+(A[N+1]-(A[r]-A[l-1]))*(X[r]-X[l-1])+(A[N+1]-(A[r]-A[l-1])-W[l-1])*(X[r]-X[l-1]))
        if (l-1, r) not in visited:
            visited.add((l-1, r))
            que.append((l-1,r))
    if r<N+1:
        dp[l][r+1][0] = min(dp[l][r+1][0],dp[l][r][0]+(A[N+1]-(A[r]-A[l-1]))*(X[r+1]-X[l])+(A[N+1]-(A[r]-A[l-1])-W[r+1])*(X[r+1]-X[l]),dp[l][r][1]+(A[N+1]-(A[r]-A[l-1]))*(X[r+1]-X[r])+(A[N+1]-(A[r]-A[l-1])-W[r+1])*(X[r+1]-X[l-1]))
        dp[l][r+1][1] = min(dp[l][r+1][1],dp[l][r][0]+(A[N+1]-(A[r]-A[l-1]))*(X[r+1]-X[l]),dp[l][r][1]+(A[N+1]-(A[r]-A[l-1]))*(X[r+1]-X[r]))
        if (l, r+1) not in visited:
            visited.add((l, r+1))
            que.append((l,r+1))
print(min(dp[1][N+1][0],dp[1][N+1][1]))