#include<bits/extc++.h>
using namespace __gnu_pbds;
using namespace std;
using ll = long long;
template <class T> constexpr auto NL(T) -> T {return std::numeric_limits<T>::max();}
template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define pb push_back
constexpr int maxn = 2010;
int dp[maxn][maxn];
void solve(void) {
    ll n, m;
    cin >> n >> m;
    memset(dp, 0x3f3f3f3f, sizeof dp);
    std::vector<ll> a1(n + 2);
    for (int i = 1; i <= n; i++) {
        cin >> a1[i];
    }
    std::vector<ll> b1(m + 2);
    for (int i = 1; i <= m; i++) {
        cin >> b1[i];
    }
    dp[n + 1][m + 1] = 0;
    for (int i = n + 1; i >= 1; i--) {
        for (int j = m + 1; j >= 1; j--) {
            if (a1[i] == b1[j] or a1[i] == 1 or b1[j] == 1) {
                dp[i][j] = min(dp[i][j], dp[i + 1][j + 1]);
            }
            dp[i][j] = min(dp[i][j], dp[i][j + 1] + 1);
            dp[i][j] = min(dp[i][j], dp[i + 1][j] + 1);
        }
    }
    int ans = NL(ans);
    for (int i = 1; i <= n + 1; i++) {
        ans = min(ans, dp[i][1]);
    }
    for (int i = 1; i <= m + 1; i++) {
        ans = min(ans, dp[1][i]);
    }
    cout << ans;
}
int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    int t = 1;
    // cin>>t;
    while (t--)
        solve();
    return 0;
}