#include <bits/stdc++.h>
using namespace std;
 
#define fi first
#define se second
#define pb push_back
using vi = vector <int>;
using ll = long long;
using vl = vector <ll>;
using pii = pair <int, int>;
const ll mod = 998244353;
//~ const ll mod = 1e9 + 7;
ll qpow(ll a, ll b, ll m = mod) { ll r = 1, t = a;
	for(; b; b /= 2) { if(b & 1) r = r * t % m; t = t * t % m; } return r; }

const int N = 4e3 + 11;
int f[N][N];

void chmin(int &a, int b) {
	if(a > b) a = b;
}

int main() {
	ios::sync_with_stdio(0);
	int n, m; cin >> n >> m;
	
	vi a, b;
	for(int i = 0; i < n; i ++) {
		int x; cin >> x;
		a.pb(0);
		for(int j = 0; j < x; j ++)
			a.pb(1);
	}
	for(int i = 0; i < m; i ++) {
		int x; cin >> x;
		b.pb(0);
		for(int j = 0; j < x; j ++)
			b.pb(1);
	}
	
	n = a.size();
	m = b.size();
	a.pb(2); b.pb(2);
	
	memset(f, 0x3f, sizeof f);
	f[0][0] = 0;
	for(int i = 0; i < n; i ++)
		for(int j = 0; j < m; j ++) {
			chmin(f[i + 1][j], f[i][j] + 1);
			chmin(f[i][j + 1], f[i][j] + 1);
			
			if(a[i + 1] == b[j + 1])
				chmin(f[i + 1][j + 1], f[i][j]);
			else
				chmin(f[i + 1][j + 1], f[i][j] + 1);
		}
	cout << f[n - 1][m - 1] << '\n';
}