#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<unordered_map>
#include<vector>
#include<bitset>
#include<queue>
#include<set>
#include<map>
#include<ctime>
#include<random>
#include<numeric>
using namespace std;
#define int long long
#define ull unsigned long long
#define lc (x<<1)
#define rc (x<<1|1)
#define pii pair<int,int>
#define mkp make_pair
#define fi first
#define se second
const int Mx=1000005,p=1e9+9,bas=233;
int read(){
	char ch=getchar();
	int Alice=0,Aya=1;
	while(ch<'0'||ch>'9'){
		if(ch=='-') Aya=-Aya;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
		Alice=(Alice<<3)+(Alice<<1)+(ch^48),ch=getchar();
	return (Aya==1?Alice:-Alice);
}
int n;
string s[2],t[2];
int pw[Mx];
int hsL[2][Mx],hsR[2][Mx];
int GetHashL(int id,int l,int r){
	return (hsL[id][r]-hsL[id][l-1]*pw[r-l+1]%p+p)%p;
}
int GetHashR(int id,int l,int r){
	return (hsR[id][l]-hsR[id][r+1]*pw[r-l+1]%p+p)%p;
}
signed main(){
	n=read();
	cin>>t[0]>>t[1];
	s[0]=" #";
	for(char c:t[0]) s[0]+=c,s[0]+='#';
	s[0]+='#';
	s[1]=" ##";
	for(char c:t[1]) s[1]+=c,s[1]+='#';
	//cout<<s[0]<<endl<<s[1]<<endl;
	n=(int)s[0].length()-1;
	pw[0]=1;
	for(int i=1;i<=n;i++) pw[i]=pw[i-1]*bas%p;
	for(int id=0;id<=1;id++) for(int i=1;i<=n;i++) hsL[id][i]=(hsL[id][i-1]*bas%p+s[id][i])%p;
	for(int id=0;id<=1;id++) for(int i=n;i>=1;i--) hsR[id][i]=(hsR[id][i+1]*bas%p+s[id][i])%p;
	int ans=0;
	for(int i=1;i<=n;i++){
		int L=0,R=min(i-1,n-i),ok=-1;
		while(L<=R){
			int mid=((L+R)>>1);
			if(GetHashR(0,i-mid,i)==GetHashL(0,i,i+mid)) L=mid+1,ok=mid;
			else R=mid-1;
		}
		int r=ok;
		L=0,R=min(i-r-1,n-i-r+1),ok=-1;
		while(L<=R){
			int mid=((L+R)>>1);
			if(GetHashR(0,i-r-mid,i-r)==GetHashL(1,i+r-1,i+r-1+mid)) L=mid+1,ok=mid;
			else R=mid-1;
		}
		r+=ok;
		ans=max(r,ans);
	}
	for(int i=1;i<=n;i++){
		int L=0,R=min(i-1,n-i),ok=-1;
		while(L<=R){
			int mid=((L+R)>>1);
			if(GetHashR(1,i-mid,i)==GetHashL(1,i,i+mid)) L=mid+1,ok=mid;
			else R=mid-1;
		}
		int r=ok;
		L=0,R=min(i-r,n-i-r),ok=-1;
		while(L<=R){
			int mid=((L+R)>>1);
			if(GetHashR(0,i-r+1-mid,i-r+1)==GetHashL(1,i+r,i+r+mid)) L=mid+1,ok=mid;
			else R=mid-1;
		}
		r+=ok;
		ans=max(r,ans);
	}
	cout<<ans;
	return 0;
}
/*
Hello!!
Sample:
6
abccba
edddda
-------------------
*/