#include <bits/stdc++.h>
using namespace std;

int main(int argc, char *argv[]) {
	int n, q;
	cin >> n >> q;
	map<int, vector<int>> A;
	for (int i = 0; i < n; i++) {
		int a;
		cin >> a;
		A[a].push_back(i);
	}
	vector<int> B(q);
	for (int j = 0; j < q; j++) {
		cin >> B[j];
	}

	//dijkstra
	//int cost = 0;
	vector<map<int, int>> cost(q + 1);
	cost[0][0] = 0;
	for (int j = 0; j < q; j++) {
		for (int i : A[B[j]]) {
			cost[j + 1][i] = INT_MIN;
		}
	}
	priority_queue<pair<int, pair<int, int>>> Q;
	Q.push( { 0, { 0, 0 } });
	while (!Q.empty()) {
		int c;
		pair<int, int> v;
		tie(c, v) = Q.top();
		Q.pop();
		int j;
		int i;
		tie(j, i) = v;
		if (j == q) {
			cout << -cost[j][i] << endl;
			break;
		}
		if (c < cost[j][i]) {
			continue;
		}
		for (int u : A[B[j]]) {
			int cst = cost[j][i] - abs(u - i);
			if (cst > cost[j + 1][u]) {
				cost[j + 1][u] = cst;
				Q.push( { cst, { j + 1, u } });
			}
		}
	}

	return 0;
}