#include <bits/stdc++.h>
#define cerr cout << "in " << __LINE__ << "\t: "
using namespace std;
#define lg(x) (31 ^ __builtin_clz(x))
int n;
string s[2], t;
const int N = 400010;
int m = 128, old[N << 1], rk[N], sa[N], cnt[N], key[N], key2[N], h[N];
int st[20][N];
int LCP(int x, int y) {
	x = rk[x], y = rk[y];
	if (x > y) swap(x, y);
	int len = lg(y - (x++));
	return min(st[len][x], st[len][y - (1 << len) + 1]);
}
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	cin >> n >> s[0] >> s[1];
	t = s[0] + '#' + s[1] + '*', n = n * 2 + 1;
	for (int i = 1; i <= n; i++) cnt[rk[i] = t[i - 1]]++;
	for (int i = 1; i <= m; i++) cnt[i] += cnt[i - 1];
	for (int i = n; i >= 1; i--) sa[cnt[rk[i]]--] = i;
	for (int w = 1;; w <<= 1) {
		int p = 0;
		for (int i = n; i > n - w; i--) key2[++p] = i;
		for (int i = 1; i <= n; i++)
			if (sa[i] > w) key2[++p] = sa[i] - w;
		memset(cnt, 0, sizeof(cnt));
		for (int i = 1; i <= n; i++) cnt[key[i] = rk[key2[i]]]++;
		for (int i = 1; i <= m; i++) cnt[i] += cnt[i - 1];
		memcpy(old, rk, sizeof(rk));
		for (int i = n; i > 0; i--) sa[cnt[key[i]]--] = key2[i];
		p = 0;
		for (int i = 1; i <= n; i++) {
			int x = sa[i], y = sa[i - 1];
			rk[sa[i]] = p += old[x] != old[y] || old[x + w] != old[y + w];
		}
		if ((m = p) == n) break;
	}
	for (int i = 1, k = 0; i <= n; ++i) {
		if (rk[i] == 1) continue;
		if (k) --k;
		while (t[i + k - 1] == t[sa[rk[i] - 1] + k - 1]) ++k;
		h[rk[i]] = k;
	}
	for (int i = 1; i <= n; i++)
		st[0][i] = h[i];
	for (int i = 1; i < 20; i++)
		for (int j = 1; j + (1 << i) - 1 <= n; j++)
			st[i][j] = min(st[i - 1][j], st[i - 1][j + (1 << i - 1)]);
	n /= 2;
	int res = 0;
	for (int i = 1; i <= (n + 1) / 2; i++) {
		for (int j = 1; j <= n; j += max(1, i - 1)) {
			if (j + i > n) continue;
			int tmp = LCP(j, j + i);
			if (tmp == 0) continue;
			if (tmp >= i) {res = i * 2; continue;}
			int tmp2 = LCP(j + tmp, j + tmp + i + n);
			if (tmp + tmp2 >= i) {res = i * 2; continue;}
			int l = j - (i - tmp - tmp2);
			if (l > 0 && LCP(l, l + i) >= i - tmp - tmp2) res = i * 2;
		}
		for (int j = 1; j <= n; j += max(1, i - 1)) {
			if (j + i > n) continue;
			int tmp = LCP(j + n + 1, j + i + n + 1);
			if (tmp == 0) continue;
			if (tmp >= i) {res = i * 2; continue;}
			int l = j - (i - tmp);
			if (l < 0) continue;
			int tmp2 = LCP(l + 1, l + n + 1 + i);
			if (tmp2 >= i - tmp) {res = i * 2; continue;}
			if (l + tmp2 <= 0) continue;
			if (LCP(l + 1 + tmp2 + n, l + 1 + tmp2 + n + i) >= i - tmp - tmp2) res = i * 2;
		}
		for (int j = 1; j <= n; j += max(1, i - 1)) {
			if (j + i - 1 > n) continue;
			int tmp = LCP(j, j + i + n);
			if (tmp == 0) continue;
			if (tmp >= i) {res = i * 2; continue;}
			int tmp2 = LCP(j + tmp + n, j + i + tmp + n);
			if (tmp2 >= i - tmp) {res = i * 2; continue;}
			int l = j - (i - tmp - tmp2);
			if (l > 0 && LCP(l, l + i + n) >= i - tmp - tmp2)
				{res = i * 2; continue;}
			l = j - (i - tmp);
			if (l <= 0) continue;
			tmp2 = LCP(l, l + i);
			if (tmp2 >= i - tmp) {res = i * 2; continue;}
			if (LCP(l + tmp2, l + tmp2 + i + n) >= i - tmp) res = i * 2;
		}
	}
	cout << res << "\n";
	return 0;
}