#include <iostream>
#include <string>
#include <unordered_map>

using namespace std;

int main() {
    int n;
    string a, b;
    cin >> n >> a >> b;

    unordered_map<char, int> h1, h2;

    for (int i = 0; i < n; i++) {
        h1[a[i]] = h1[a[i]] + 1;
    }

    for (int i = 0; i < n; i++) {
        h2[b[i]] = h2[b[i]] + 1;
    }

    int check = 0;
    for (char c = 'a'; c <= 'z'; c++) {
        if (h1[c] != h2[c]) {
            check = 1;
            break;
        }
    }

    if (check == 1) {
        cout << "Answer not possible." << endl;
    } else {
        int r = 0;
        int i = n - 1;
        int j = n - 1;
        while (i >= 0 && j >= 0) {
            if (a[i] == b[j]) {
                r = r + 1;
                i = i - 1;
                j = j - 1;
            } else {
                i = i- 1;
            }
        }
        cout << n - r << endl;
    }

    return 0;
}