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

using i64 = long long;

constexpr double PI = numbers::pi;

void dft(vector<complex<double>> &a) {
    int n = a.size();
    if (n == 1) { return; }
    vector<int> rev(n);
    int k = __builtin_ctz(n) - 1;
    for (int i = 0; i < n; i++) {
        rev[i] = rev[i >> 1] >> 1 | (i & 1) << k;
        if (rev[i] < i) {
            swap(a[rev[i]], a[i]);
        }
    }
    vector<complex<double>> roots(n);
    for (int i = 0; i < n; i++) {
        roots[i] = exp(2 * PI / n * i * complex<double>(0, 1));
    }
    for (int k = 1; k < n; k *= 2) {
        for (int i = 0; i < n; i += 2 * k) {
            for (int j = 0; j < k; j++) {
                auto u = a[i + j], v = a[i + j + k] * roots[n / (2 * k) * j];
                a[i + j] = u + v;
                a[i + j + k] = u - v;
            }
        }
    }
}

void idft(vector<complex<double>> &a) {
    int n = a.size();
    reverse(a.begin() + 1, a.end());
    dft(a);
    for (int i = 0; i < n; i++) {
        a[i] /= n;
    }
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    
    auto solve = [&]() {
        int n;
        cin >> n;

        string s, t;
        cin >> s >> t;
        s += s;
        reverse(t.begin(), t.end());

        int sz = 1;
        while (sz < 3 * n - 1) {
            sz *= 2;
        }

        constexpr int A = 26;

        vector a(A, vector<complex<double>>(sz)), b(a);
        for (int c = 0; c < A; c++) {
            for (int i = 0; i < 2 * n; i++) {
                if (s[i] - 'a' == c) {
                    a[c][i] = 1;
                }
            }
            for (int i = 0; i < n; i++) {
                if (t[i] - 'a' == c) {
                    b[c][i] = 1;
                }
            }
            dft(a[c]);
            dft(b[c]);
        }

        int ans = n + 1;

        for (int c = 0; c < A; c++) {
            vector<complex<double>> res(sz);
            for (int i = 0; i < A; i++) {
                int j = (i + c) % A;
                for (int x = 0; x < sz; x++) {
                    res[x] += a[i][x] * b[j][x];
                }
            }
            idft(res);
            int match = 0;
            for (int i = 0; i < n; i++) {
                int x = round(res[i + n - 1].real());
                match = max(match, x);
            }
            ans = min(ans, n - match);
        }
        
        cout << ans << '\n';
    };

    solve();

    return 0;
}