n, m = map(int,input().split())
a = list(map(int,input().split()))
b = list(map(int,input().split()))
s = []
t = []
for i in range(n):
    for _ in range(a[i]):
        s.append(1)
    s.append(0)
for i in range(m):
    for _ in range(b[i]):
        t.append(1)
    t.append(0)
s = ''.join(map(str, s));t = ''.join(map(str, t))
n = len(s)
m = len(t)
dp = [[0] * (m + 1) for _ in range(n + 1)]
for i in range(n + 1):
    dp[i][0] = i
for j in range(m + 1):
    dp[0][j] = j
for i in range(1, n + 1):
    for j in range(1, m + 1):
        dp[i][j] = min(dp[i - 1][j] + 1, dp[i][j - 1] + 1, dp[i - 1][j - 1] + (s[i - 1] != t[j - 1]))
print(dp[n][m])