n, m = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
S = []
for a in A:
    S += [0] + [1] * a
T = []
for b in B:
    T += [0] + [1] * b
ls = len(S)
lt = len(T)
dp = [[1 << 30] * (lt + 1) for _ in range(ls + 1)]
dp[0][0] = 0

for i in range(1, ls + 1):
    for j in range(1, lt + 1):
        dp[i][j] = min(dp[i - 1][j] + 1, dp[i][j - 1] + 1)
        if S[i - 1] == T[j - 1]:
            dp[i][j] = min(dp[i][j], dp[i - 1][j - 1])
        else:
            dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + 1)

print(dp[ls][lt])