#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
const int N = 1e5 + 5;
int n; string s, t;
struct Node {
	int p, x; string s;
};
queue<Node> q;
map<string, int> m;
signed main() {
	cin>>n>>s>>t;
	s += "**", t += "**";
	q.push({0, n, s});
	while(!q.empty()) {
		auto f = q.front(); q.pop();
		// cout<<f.s<<" "<<f.p<<endl;
		if(f.s == t) cout<<f.p<<endl, exit(0);
		for(int i = 0; i < n + 1; i++) if(i != f.x && i + 1 != f.x) {
			string d = f.s; 
			swap(d[i], d[f.x]), swap(d[i + 1], d[f.x + 1]);
			if(m[d]) continue; m[d] = 1;
			q.push({f.p + 1, i, d});
		}
	}
	cout<<-1<<endl;
}