#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 5;
const ll rdx = 311, MOD = 998244353;
int n;
char s[2][maxn];
ll pw[maxn], hsh[2][maxn], revhsh[2][maxn];
ll getseg(int rw, int l, int r) {
	if (l <= 0 || r > n) {
		return -2;
	}
	return ((hsh[rw][r] - hsh[rw][l - 1] * pw[r - l + 1]) % MOD + MOD) % MOD;
}
ll getrevseg(int rw, int l, int r) {
	if (l <= 0 || r > n) {
		return -1;
	}
	return ((revhsh[rw][l] - revhsh[rw][r + 1] * pw[r - l + 1]) % MOD + MOD) % MOD;
}
int main() {
	scanf("%d %s %s", &n, s[0] + 1, s[1] + 1);
	pw[0] = 1;
	for (int i = 1; i <= n; i++) {
		pw[i] = pw[i - 1] * rdx % MOD;
	}
	for (int i = 0; i < 2; i++) {
		for (int j = 1; j <= n; j++) {
			hsh[i][j] = (hsh[i][j - 1] * rdx + s[i][j]) % MOD;
		}
		for (int j = n; j >= 1; j--) {
			revhsh[i][j] = (revhsh[i][j + 1] * rdx + s[i][j]) % MOD;
		}
	}
	int ans = 0;
	{
		for (int rw = 0; rw < 2; rw++) {
			for (int i = 1; i <= n; i++) {
				int lb = 0, ub = n, res1;
				while (lb <= ub) {
					int mid = (lb + ub) >> 1;
					if (getseg(rw, i - mid, i + mid) == getrevseg(rw, i - mid, i + mid)) {
						res1 = mid;
						lb = mid + 1;
					} else {
						ub = mid - 1;
					}
				}
				lb = 0, ub = n;
				int res2;
				while (lb <= ub) {
					int mid = (lb + ub) >> 1;
					if (getseg(0, i - res1 - mid + rw, i - res1 - 1 + rw) == getrevseg(1, i + res1 + rw, i + res1 + mid - 1 + rw)) {
						res2 = mid;
						lb = mid + 1;
					} else {
						ub = mid - 1;
					}
				}
				ans = max(ans, (res1 + res2) * 2 + 1);
			}
		}
	}
	{
		for (int rw = 0; rw < 2; rw++) {
			for (int i = 1; i <= n; i++) {
				int lb = 0, ub = n, res1;
				while (lb <= ub) {
					int mid = (lb + ub) >> 1;
					if (getseg(rw, i - mid + 1, i + mid) == getrevseg(rw, i - mid + 1, i + mid)) {
						res1 = mid;
						lb = mid + 1;
					} else {
						ub = mid - 1;
					}
				}
				lb = 0, ub = n;
				int res2;
				while (lb <= ub) {
					int mid = (lb + ub) >> 1;
					if (getseg(0, i - res1 + 1 - mid + rw, i - res1 + rw) == getrevseg(1, i + res1 + rw, i + res1 + mid - 1 + rw)) {
						res2 = mid;
						lb = mid + 1;
					} else {
						ub = mid - 1;
					}
				}
				ans = max(ans, (res1 + res2) * 2);
			}
		}
	}
	printf("%d\n", ans);
	return 0;
}