N,M=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
a=[]
b=[]
for i in A:
    a+=["o"]*i+["|"]
a=a[:-1]
for i in B:
    b+=["o"]*i+["|"]
b=b[:-1]
n=len(a)
m=len(b)
dp=[[1<<60]*(m+1) for i in range(n+1)]
dp[0][0]=0
for i in range(n+1):
    for j in range(m+1):
        if i!=n:
            dp[i+1][j]=min(dp[i+1][j],dp[i][j]+1)
        if j!=m:
            dp[i][j+1]=min(dp[i][j+1],dp[i][j]+1)
        if i!=n and j!=m:
            dp[i+1][j+1]=min(dp[i+1][j+1],dp[i][j]+1)
            if a[i]==b[j]:
                dp[i+1][j+1]=min(dp[i+1][j+1],dp[i][j])
print(dp[n][m])