#include<bits/stdc++.h>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>
#include <math.h>
#include <cstdio>
#define int long long
using namespace std;
const int Base=19260817;
const int mod=1e9+7;
const int N=1e5+5;
int n,base[N],ha[N],hb[N],qa[N],qb[N],ans;
string a,b;
int read(){
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}
int geth(int l,int r,int op){
	if(!op)return (ha[r]-ha[l-1]*base[r-l+1]%mod+mod)%mod;
	return (hb[r]-hb[l-1]*base[r-l+1]%mod+mod)%mod;
}
int getq(int l,int r,int op){
	if(!op)return (qa[l]-qa[r+1]*base[r-l+1]%mod+mod)%mod;
	return (qb[l]-qb[r+1]*base[r-l+1]%mod+mod)%mod;
}
void solve(){
	for(int i=1;i<=n;i++){//cout<<"!!!!"<<i<<endl;
		int aaa=0;
		int l=1,r=min(i,n-i+1);
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-mid+1,i,0)==getq(i,i+mid-1,1))aaa=mid,l=mid+1;
			else r=mid-1; 
		}
		ans=max(ans,2*aaa);
		l=1,r=min(i-1,n-i),aaa=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-mid,i+mid,0)==getq(i-mid,i+mid,0))aaa=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*aaa+1); 
		//[i-aaa,i+aaa]
		l=1,r=min(i-aaa-1,n-(i+aaa-1));int bbb=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-aaa-mid,i-aaa-1,0)==getq(i+aaa,i+aaa+mid-1,1))bbb=mid,l=mid+1;
			else r=mid-1;
		} 
		ans=max(ans,2*(aaa+bbb)+1);
		if(i==n||a[i-1]!=a[i])continue;
		l=1,r=min(i-1,n-(i+1));aaa=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-mid,i+1+mid,0)==getq(i-mid,i+1+mid,0))aaa=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*(aaa+1));bbb=0;
		//[i-aaa,i+1+aaa]
		l=1,r=min(i-aaa-1,n-(i+aaa));
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-aaa-mid,i-aaa-1,0)==getq(i+1+aaa,i+1+aaa+mid-1,1))bbb=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*(aaa+bbb+1));//cout<<"!"<<aaa<<" "<<bbb<<endl;
	}
}
void solveb(){
	for(int i=1;i<=n;i++){//cout<<"!!!!"<<i<<endl;
		int l=1,r=min(i-1,n-i),aaa=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-mid,i+mid,1)==getq(i-mid,i+mid,1))aaa=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*aaa+1); 
		l=1,r=min(i-aaa,n-(i+aaa));int bbb=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-aaa-mid+1,i-aaa,0)==getq(i+aaa+1,i+aaa+mid,1))bbb=mid,l=mid+1;
			else r=mid-1;
		} 
		ans=max(ans,2*(aaa+bbb)+1);
		if(i==n||b[i-1]!=b[i])continue;
		l=1,r=min(i-1,n-(i+1));aaa=0;
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-mid,i+1+mid,1)==getq(i-mid,i+1+mid,1))aaa=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*(aaa+1));bbb=0;
		l=1,r=min(i-aaa,n-(i+aaa+1));
		while(l<=r){
			int mid=(l+r)>>1;
			if(geth(i-aaa-mid+1,i-aaa,0)==getq(i+1+aaa+1,i+1+aaa+mid,1))bbb=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,2*(aaa+bbb+1));//cout<<"!"<<aaa<<" "<<bbb<<" "<<2*(aaa+bbb+1)<<endl;
	}
}
signed main(){
	//freopen("data.in","r",stdin);
	//ios::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
	n=read();
	cin>>a>>b;
	base[0]=1;for(int i=1;i<=n;i++)base[i]=base[i-1]*Base,base[i]%=mod;
	for(int i=1;i<=n;i++)ha[i]=ha[i-1]*Base%mod+a[i-1]-'a'+1,ha[i]%=mod;
	for(int i=1;i<=n;i++)hb[i]=hb[i-1]*Base%mod+b[i-1]-'a'+1,hb[i]%=mod;
	for(int i=n;i>=1;i--)qa[i]=qa[i+1]*Base%mod+a[i-1]-'a'+1,qa[i]%=mod;
	for(int i=n;i>=1;i--)qb[i]=qb[i+1]*Base%mod+b[i-1]-'a'+1,qb[i]%=mod;
	solve();
	solveb();
	cout<<ans;
	return 0;
}