#include<bits/stdc++.h>
using namespace std;

int n;
string s[2];
#define ull unsigned long long

ull bas=131,mod=998244853,pw[100100];
ull hsz[2][100100],hsf[2][100100];

void ini(){
	pw[0]=1;
	for(int i=1;i<=n;i++) pw[i]=pw[i-1]*bas;
	for(int j=0;j<2;j++){
		for(int i=1;i<=n;i++) hsz[j][i]=hsz[j][i-1]*bas+s[j][i];
	}
	for(int i=0;i<2;i++){
		for(int j=n;j>=1;j--){
			hsf[i][j]=hsf[i][j+1]*bas+s[i][j];	
		}
	}
}


inline ull get_hs0(int id,int l,int r){return hsz[id][r]-hsz[id][l-1]*pw[r-l+1];}
inline ull get_hs1(int id,int l,int r){return hsf[id][l]-hsf[id][r+1]*pw[r-l+1];}
inline ull get_hs(int id,int l,int r,bool type){return l>r?0:type?get_hs1(id,l,r):get_hs0(id,l,r);}


int main(){
	cin>>n;
	cin>>s[0];
	cin>>s[1];
	s[0]=" "+s[0];
	s[1]=" "+s[1];
	ini();
	int ans=1;
	for(int i=1;i<=n;i++){
		int l=1,r=min(i,n-i+1);
		while(l<r){
			int mid=(l+r-1)/2+1;
			if(get_hs(0,i-mid+1,i+mid-1,0)==get_hs(0,i-mid+1,i+mid-1,1)) l=mid;
			else r=mid-1;
		}
		ans=max(ans,l*2-1);
		int L=l,R=min(i,n-i+2);
		while(L<R){
			int mid=(L+R-1)/2+1;
			if(get_hs(0,i-mid+1,i-l,0)==get_hs(1,i+l-1,i+mid-2,1)) L=mid;
			else R=mid-1;
		}
		ans=max(ans,L*2-1);
		
		l=1,r=min(i,n-i+1);
		while(l<r){
			int mid=(l+r-1)/2+1;
			if(get_hs(1,i-mid+1,i+mid-1,0)==get_hs(1,i-mid+1,i+mid-1,1)) l=mid;
			else r=mid-1;
		}
		ans=max(ans,l*2-1);
		L=l,R=min(i+1,n-i+1);
		while(L<R){
			int mid=(L+R-1)/2+1;
			if(get_hs(0,i-mid+2,i-l+1,0)==get_hs(1,i+l,i+mid-1,1)) L=mid;
			else R=mid-1;
		}
		ans=max(ans,L*2-1);
		
		l=0,r=min(i,n-i);
		while(l<r){
			int mid=(l+r-1)/2+1;
			if(get_hs(0,i-mid+1,i+mid,0)==get_hs(0,i-mid+1,i+mid,1)) l=mid;
			else r=mid-1; 
		}
		ans=max(ans,l*2);
		L=l,R=min(i,n-i+1);
		while(L<R){
			int mid=(L+R-1)/2+1;
			if(get_hs(0,i-mid+1,i-l,0)==get_hs(1,i+l,i+mid-1,1)) L=mid;
			else R=mid-1;
		}
		ans=max(ans,L*2);
		
		l=0,r=min(i,n-i);
		while(l<r){
			int mid=(l+r-1)/2+1;
			if(get_hs(1,i-mid+1,i+mid,0)==get_hs(1,i-mid+1,i+mid,1)) l=mid;
			else r=mid-1;
		}
		ans=max(ans,l*2);
		L=l,R=min(i+1,n-i);
		while(L<R){
			int mid=(L+R-1)/2+1;
			if(get_hs(0,i-mid+2,i-l+1,0)==get_hs(1,i+l+1,i+mid,1)) L=mid;
			else R=mid-1;
		}
		ans=max(ans,L*2);
		
		l=1,r=min(i,n-i+1);
		while(l<r){
			int mid=(l+r-1)/2+1;
			if(get_hs(0,i-mid+1,i,0)==get_hs(1,i,i+mid-1,1)) l=mid;
			else r=mid-1;
		}
		ans=max(ans,l*2);
		
	}
	cout<<ans<<endl; 
	
	return 0;
}

/*
14
abaabababffaba
yiuydbaabakjgj

9
abcdedcff
asdgafbaf

9
abcfjkuiy
ffdedcbaf
*/