#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define eb emplace_back
#define se second
#define fi first
//	freopen("date.in.txt","r",stdin);
//    freopen("date.out.txt","w",stdout);
//clock_t start, stop;
//	start = clock();
//	stop = clock();
//	double time = (double(stop - start) / CLK_TCK);
//	cout << fixed << setprecision(6) << time << "\n";
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef unsigned long long ull;
constexpr ll LNF = 0x3f3f3f3f3f3f3f3f;						
constexpr int INF = 0x3f3f3f3f;
constexpr int mod = 1e9 + 7;
constexpr int maxn = 1e5 + 10, P = 13331;

int m, n, p[2010], q[2010], f[2010][2010], ans = INF; 

void solve()
{
	cin >> m >> n;
	for(int i = 1; i <= m; i ++) cin >> p[i];
	for(int i = 1; i <= n; i ++) cin >> q[i];
	memset(f, INF, sizeof(f));
	f[m][n] = 0;
	for(int i = m; i >= 1; i --)
	{
		for(int j = n; j >= 1; j --)
		{
			if(p[i] == q[j] || p[i] == 1 || q[j] == 1)
				f[i - 1][j - 1] = min(f[i - 1][j - 1], f[i][j]);
			
			f[i - 1][j] = min(f[i - 1][j], f[i][j] + 1);
			f[i][j - 1] = min(f[i][j - 1], f[i][j] + 1);
		}
	}
	for(int i = 0; i < n; i ++) ans = min(ans, f[0][i]);
	for(int i = 0; i < m; i ++) ans = min(ans, f[i][0]);
	cout << ans;
}

int main()
{
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
//	freopen("date.in.txt","r",stdin);
//	freopen("date.out.txt","w",stdout);
	
	int T = 1;
//	cin >> T;
	while(T --)
	{
		solve();
	}
	
	return 0;
}