N, Q = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
from collections import defaultdict

dic = defaultdict(list)
for i, a in enumerate(A):
    dic[a].append(i)
INF = 10 ** 6

from atcoder.segtree import SegTree
base = [INF] * N
ST1a = SegTree(min, INF, base)
ST2a = SegTree(min, INF, base)
ST1a.set(0, 0)
ST2a.set(0, 0)

for b in B:
    ST1b = SegTree(min, INF, base)
    ST2b = SegTree(min, INF, base)
    BB = [-1] * N
    for c in dic[b]:
        a = ST1a.prod(c, N) - c
        a = min(a, ST2a.prod(0, c) + c)
        #BB[c] = a
        ST1b.set(c, a + c)
        ST2b.set(c, a - c)
    #print(BB)
    ST1a = ST1b
    ST2a = ST2b

ans = INF
for i in range(N):
    ans = min(ans, ST1a.get(i) - i, ST2a.get(i) + i)
print(ans)