#include <bits/stdc++.h>

using namespace std;
const int N = 2e5 + 10;
using ll = long long;
ll p[N], q[N];

int main() {
    ll n, m;
    cin >> m >> n;
    if (m >= n) {
        for (int i = 1; i <= m; i++) cin >> p[i];
        for (int i = 1; i <= n; i++) cin >> q[i];
    } else {
        for (int i = 1; i <= m; i++) cin >> q[i];
        for (int i = 1; i <= n; i++) cin >> p[i];
        swap(n, m);
    }

    for (int i = 1; i <= m / 2; i++) swap(p[i], p[m - i + 1]);
    for (int i = 1; i <= n / 2; i++) swap(q[i], q[n - i + 1]);

    vector<vector<ll>> dp(m + 2, vector<ll>(n + 2, 1e18));
    dp[0][0] = 0;
    ll ans = n;
    for (int i = 1; i <= m + 1; i++) {
        for (int j = 1; j <= n; j++) {
            dp[i][j] = j;
            if (p[i] == q[j] || p[i] == 1 || q[j] == 1)
                dp[i][j] = min(dp[i][j], dp[i - 1][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);
        }
        ans = min(ans, dp[i][n]);
    }
    cout << ans << "\n";
}