from sys import stdin

def main():
    n, m = map(int, stdin.readline().split())
    a = list(map(int, stdin.readline().split()))
    b = list(map(int, stdin.readline().split()))
    aa = []
    for i in range(n):
        aa += [0] * a[i]
        if i != n - 1:
            aa += [1]
    bb = []
    for i in range(m):
        bb += [0] * b[i]
        if i != m - 1:
            bb += [1]
    dp = [[0 for j in range(len(bb) + 1)] for i in range(len(aa) + 1)]
    for i in range(len(aa) + 1):
        dp[i][0] = i
    for i in range(len(bb) + 1):
        dp[0][i] = i
    for i in range(len(aa)):
        for j in range(len(bb)):
            dp[i + 1][j + 1] = min([dp[i + 1][j] + 1, dp[i][j] + (aa[i] != bb[j]), dp[i][j + 1] + 1])
    print(dp[len(aa)][len(bb)])
 
if __name__ == '__main__':
    main()