def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    
    idx = 0
    N = int(data[idx])
    M = int(data[idx+1])
    idx += 2
    
    A = list(map(int, data[idx:idx+N]))
    idx += N
    B = list(map(int, data[idx:idx+M]))
    idx += M
    
    prefix_A = [0] * (N + 1)
    for i in range(1, N+1):
        prefix_A[i] = prefix_A[i-1] + A[i-1]
    
    prefix_B = [0] * (M + 1)
    for i in range(1, M+1):
        prefix_B[i] = prefix_B[i-1] + B[i-1]
    
    INF = float('inf')
    dp = [ [INF] * (M+1) for _ in range(N+1) ]
    dp[0][0] = 0
    
    for j in range(1, M+1):
        for i in range(1, N+1):
            for k in range(i):
                S = prefix_A[i] - prefix_A[k]
                d = B[j-1]
                required = d - S
                if required < 0:
                    continue
                max_possible = (i - k -1)
                if required > max_possible:
                    continue
                cost = (i - k -1) + required
                if dp[k][j-1] + cost < dp[i][j]:
                    dp[i][j] = dp[k][j-1] + cost
    
    print(dp[N][M])

if __name__ == '__main__':
    main()