#include <bits/stdc++.h>
#define X first
#define Y second
using namespace std;
using ld = double;
typedef unsigned long long int ll;
using pii = pair<int, int>;
const int maxn = 2e5 + 10, bs = 137;
int n, f[maxn]; char s[2][maxn], t[2][maxn]; int ans = 0; ll h[2][maxn], rh[2][maxn], pw[maxn];
inline int hs(int o, int l, int r) { return h[o][r] - h[o][l - 1] * pw[r - l + 1]; }
inline int rhs(int o, int l, int r) { return rh[o][l] - rh[o][r + 1] * pw[r - l + 1]; }
inline void solve() {
    for (int i = 1; i <= n; i++) pw[i] = pw[i - 1] * bs;
    for (int o = 0; o <= 1; o++) {
        for (int i = 1, j = n; i <= n; i++, j--) {
            h[o][i] = h[o][i - 1] * bs + s[o][i];
            rh[o][j] = rh[o][j + 1] * bs + s[o][j];
        }
    }
    for (int i = 1; i <= n; i++) {
        int l = 0, r = min(i, n - i + 1) + 1;
        while (l < r) {
            int mid = l + r >> 1;
            if (hs(0, i - mid + 1, i) == rhs(0, i, i + mid - 1)) l = mid + 1;
            else r = mid;
        }
        f[i] = l - 1;
        //cout << f[i] << " ";
    }
    //cout << "\n";
    for (int i = 1; i <= n; i++) {
        int l = 0, r = min(i - f[i], n - i - f[i] + 1) + 1;
        while (l < r) {
            int mid = l + r >> 1;
            if (hs(0, i - f[i] - mid + 1, i - f[i]) == rhs(1, i + f[i], i + f[i] + mid - 1)) l = mid + 1;
            else r = mid;
        }
        ans = max(ans, f[i] + l - 2);
    }
}
int main() {
    scanf("%d%s%s", &n, t[0] + 1, t[1] + 1); pw[0] = 1;
    for (int i = 1; i <= n; i++) s[0][i * 2] = t[0][i], s[0][i * 2 + 1] = '#'; 
    for (int i = 1; i <= n; i++) s[1][i * 2 + 2] = t[1][i], s[1][i * 2 + 1] = '#';
    n = n * 2 + 3; s[0][1] = s[1][1] = s[0][n] = s[1][n] = '#'; solve(); swap(s[0], s[1]);
    reverse(s[0] + 1, s[0] + n + 1), reverse(s[1] + 1, s[1] + n + 1);
    solve(); printf("%d\n", ans);
    return 0; 
}