class SegmentTree:
    def __init__(self,
                n,
                identity_e,
                combine_f,
                ):
        self._n = n
        self._size = 1
        while self._size < self._n:
            self._size <<= 1
        self._identity_e = identity_e
        self._combine_f = combine_f
        self._node = [self._identity_e] * (2 * self._size)

    def build(self, array):
        assert len(array) == self._n
        for index, value in enumerate(array, start=self._size):
            self._node[index] = value
        for index in range(self._size - 1, 0, -1):
            self._node[index] = self._combine_f(
                self._node[index << 1 | 0],
                self._node[index << 1 | 1]
            )

    def update(self, index, value):
        i = self._size + index
        self._node[i] = value
        while i > 1:
            i >>= 1
            self._node[i] = self._combine_f(
                self._node[i << 1 | 0],
                self._node[i << 1 | 1]
            )

    def fold(self, L, R):
        L += self._size
        R += self._size
        value_L = self._identity_e
        value_R = self._identity_e
        while L < R:
            if L & 1:
                value_L = self._combine_f(value_L, self._node[L])
                L += 1
            if R & 1:
                R -= 1
                value_R = self._combine_f(self._node[R], value_R)
            L >>= 1
            R >>= 1
        return self._combine_f(value_L, value_R)

    def get(self, p):
        return self._node[p + self._size]

    def max_right(self, l, f):
        assert 0 <= l <= self._n
        assert f(self._identity_e)
        if l == self._n:
            return self._n
        l += self._size
        sm = self._identity_e
        while True:
            while l % 2 == 0:
                l >>= 1
            if not f(self._combine_f(sm, self._node[l])):
                while l < self._size:
                    l <<= 1
                    if f(self._combine_f(sm, self._node[l])):
                        sm = self._combine_f(sm, self._node[l])
                        l += 1
                return l - self._size
            sm = self._combine_f(sm, self._node[l])
            l += 1
            if l & -l == l:
                break
        return self._n

    def min_left(self, r, f):
        assert 0 <= r <= self._n
        assert f(self._identity_e)
        if r == 0:
            return 0
        r += self._size
        sm = self._identity_e
        while True:
            r -= 1
            while r > 1 and r % 2:
                r >>= 1
            if not f(self._combine_f(self._node[r], sm)):
                while r < self._size:
                    r = 2 * r + 1
                    if f(self._combine_f(self._node[r], sm)):
                        sm = self._combine_f(self._node[r], sm)
                        r -= 1
                return r + 1 - self._size
            sm = self._combine_f(self._node[r], sm)
            if r & -r == r:
                break
        return 0

    def __str__(self):
        temp = []
        for i in range(self._n):
            temp.append(str(self.fold(i, i + 1)))
        return ' '.join(temp)



N, Q = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

Tp = SegmentTree(N, 10 ** 18, min)
Tm = SegmentTree(N, 10 ** 18, min)
Tp.update(0, 0)
Tm.update(0, 0)
for b in B:
    nTp = SegmentTree(N, 10 ** 18, min)
    nTm = SegmentTree(N, 10 ** 18, min)
    for i, a in enumerate(A):
        if b == a:
            vm = Tm.fold(0, i + 1) + i
            vp = Tp.fold(i, N) - i
            ans = min(vp, vm)
            nTp.update(i, min(ans + i, nTp.fold(i, i + 1)))
            nTm.update(i, min(ans - i, nTm.fold(i, i + 1)))
    Tp, nTp = nTp, Tp
    Tm, nTm = nTm, Tm
    
ans = 10 ** 18
for i in range(N):
    ans = min(ans, Tp.fold(i, i + 1) - i)
    ans = min(ans, Tm.fold(i, i + 1) + i)
    
print(ans)