import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        int nCount = 0;
        HashSet<Integer> nSet = new HashSet<>();
        for (int i = 0; i < n; i++) {
            nSet.add(nCount);
            nCount += sc.nextInt() + 1;
        }
        int mCount = 0;
        HashSet<Integer> mSet = new HashSet<>();
        for (int i = 0; i < m; i++) {
            mSet.add(mCount);
            mCount += sc.nextInt() + 1;
        }
        int[][] dp = new int[nCount+1][mCount+1];
        for (int[] arr : dp) {
            Arrays.fill(arr, Integer.MAX_VALUE);
        }
        dp[0][0] = 0;
        for (int i = 0; i < nCount; i++) {
            for (int j = 0; j < mCount; j++) {
                if (nSet.contains(i) == mSet.contains(j)) {
                    dp[i + 1][j + 1] = Math.min(dp[i + 1][j + 1], dp[i][j]);
                }
                dp[i + 1][j] = Math.min(dp[i + 1][j], dp[i][j] + 1);
                dp[i][j + 1] = Math.min(dp[i][j + 1], dp[i][j] + 1);
            }
        }
        System.out.println(dp[nCount][mCount]);
    }
    
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}