#include<bits/stdc++.h>
#define M 100005
using namespace std;
char s[2][M];
using ull = unsigned long long;
int n;
ull pw[M], bs = 131, hsh[2][M], bsh[2][M];
ull get(int l, int r, int di, int mks)
{
	if(di) return hsh[mks][r] - hsh[mks][l - 1] * pw[r - l + 1];
	return bsh[mks][l] - bsh[mks][r + 1] * pw[r - l + 1];
}
int solve(int L, int R)
{
	int l = 0, r = min(L, n - R + 1), mid, ret = -1;
	while(l <= r)
	{
		mid = (l + r) >> 1;
		if(get(L - mid + 1, L, 1, 0) == get(R, R + mid - 1, 0, 1)) ret = mid, l = mid + 1;
		else r = mid - 1; 
	}
	return ret;
}
int main()
{
	scanf("%d", &n);
	scanf("%s%s", s[0] + 1, s[1] + 1);
	pw[0] = 1;
	for(int i = 1; i <= n; i++) pw[i] = pw[i - 1] * bs;
	for(int i = 1; i <= n; i++) for(int j = 0; j < 2; j++) hsh[j][i] = hsh[j][i - 1] * bs + s[j][i];
	for(int i = n; i >= 1; i--) for(int j = 0; j < 2; j++) bsh[j][i] = bsh[j][i + 1] * bs + s[j][i];
	int ans = 0;
	for(int i = 1; i <= n; i++) for(int j = 0; j < 2; j++)
	{
		int l = 0, r = min(i - 1, n - i), mid, ret = -1;
		while(l <= r)
		{
			mid = (l + r) >> 1;
			if(get(i - mid, i, 1, j) == get(i, i + mid, 0, j)) ret = mid, l = mid + 1;
			else r = mid - 1;
		}
		ans = max(ans, 1 + 2 * (ret + (j == 0 ? solve(i - ret - 1, i + ret) : solve(i - ret, i + ret + 1))));
	}
	for(int i = 1; i < n; i++) for(int j = 0; j < 2; j++)
	{
		int l = 0, r = min(i, n - i), mid, ret = -1;
		while(l <= r)
		{
			mid = (l + r) >> 1;
			if(get(i - mid + 1, i, 1, j) == get(i + 1, i + mid, 0, j)) ret = mid, l = mid + 1;
			else r = mid - 1;
		}
		ans = max(ans, 2 * (ret + (j == 0 ? solve(i - ret, i + ret) : solve(i - ret + 1, i + ret + 1))));
	}
	printf("%d\n", ans);
	return 0;
}