#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

using ull = unsigned long long;

const int N = 200010;

int n, ans, R[N];
ull pw[N], f[N], g[N];
char S[N], T[N];

void solve(char S[], char T[]) {
    for (int i = 1; i <= n; i++) f[i] = f[i - 1] * 131 + S[i];
    for (int i = n; i >= 1; i--) g[i] = g[i + 1] * 131 + T[i];
	for (int i = 1, m = 1, r = 1; i <= n; i++) {
        R[i] = min(r - i + 1, R[m * 2 - i]);
        while (S[i - R[i]] == S[i + R[i]]) ++R[i];
        if (i + R[i] - 1 > r) m = i, r = i + R[i] - 1;
    }
	for (int i = 1; i <= n; i++) {
        int j = max(ans + 1, R[i]);
		while (j + 1 <= i &&
			f[i - R[i]] - f[i - j - 1] * pw[j - R[i] + 1] ==
			g[i + R[i] - 2] - g[i + j - 1] * pw[j - R[i] + 1]
		) ++j;
        ans = max(ans, j - 1);
    }
}

signed main() {
    scanf("%d", &n);
    static char str[N];
    scanf("%s", str + 1), S[0] = '(', S[1] = '#';
    for (int i = 1; i <= n; ++i) S[i << 1] = str[i], S[i << 1 | 1] = '#';
    scanf("%s", str + 1), T[0] = '(', T[1] = '#';
    for (int i = 1; i <= n; ++i) T[i << 1] = str[i], T[i << 1 | 1] = '#';
    n = 2 * n + 1, pw[0] = 1;
    for (int i = 1; i <= n; ++i) pw[i] = pw[i - 1] * 131;
    solve(S, T);
    reverse(S + 1, S + n + 1), reverse(T + 1, T + n + 1);
    solve(T, S);
    printf("%d", ans);
    return 0;
}