#include <bits/stdc++.h>
using namespace std;
const int bs=233;
struct HS{
	string s;
	int n;
	__int128 hs[200005],rhs[200005],p[200005];
	void read(){
		cin>>s;
		n=s.size();
		s=' '+s;
		p[0]=1;
		for(int i=1;i<=n;i++) {
			hs[i]=hs[i-1]*bs+(s[i]-'a');
			p[i]=p[i-1]*bs;
		}
		for(int i=n;i;i--)rhs[i]=rhs[i+1]*bs+(s[i]-'a');
	}
	void init(){
		s=s.substr(1);
		reverse(s.begin(),s.end());
		s=' '+s;
		p[0]=1;
		for(int i=1;i<=n;i++) {
			hs[i]=hs[i-1]*bs+(s[i]-'a');
			p[i]=p[i-1]*bs;
		}
		for(int i=n;i;i--)rhs[i]=rhs[i+1]*bs+(s[i]-'a');
	}
	unsigned long long HSS(int l,int r){
		return hs[r]-hs[l-1]*p[r-l+1];
	}
	unsigned long long RHSS(int l,int r){
		return rhs[l]-rhs[r+1]*p[r-l+1];
	}
}Hash[2];
int ans=0,n;
void solve(){//cout<<1;
	for(int i=1;i<=n;i++){
		int l=0,r=min(i,n-i+1),nw=0;
		while(l<=r){
			int mid=l+r>>1;
			if(Hash[0].HSS(i-mid+1,i)==Hash[1].RHSS(i,i+mid-1)){
				nw=mid;
				l=mid+1;
			}else r=mid-1;
		}
		ans=max(ans,nw*2);
	}
	for(int i=1;i<=n;i++){
		int l=0,r=min(i,n-i+1),nw=0;
		while(l<=r){
			int mid=l+r>>1;
			if(Hash[0].HSS(i-mid+1,i)==Hash[0].RHSS(i,i+mid-1)){
				nw=mid;
				l=mid+1;
			}else r=mid-1;
		}
		int nl=i-nw,nr=i+nw-1;
		l=0,r=min(nl,n-nr+1),nw=0;
		while(l<=r){
			int mid=l+r>>1;
			if(Hash[0].HSS(nl-mid+1,nl)==Hash[1].RHSS(nr,nr+mid-1)){
				nw=mid;
				l=mid+1;
			}else r=mid-1;
		}
		ans=max(ans,nw*2+nr-nl);
		if(Hash[0].HSS(i,i)!=Hash[0].RHSS(i,i)){
			while(1)cout<<i<<' '<<Hash[0].HSS(i,i)<<' '<<Hash[0].RHSS(i,i)<<'\n';
		}
	}
	for(int i=1;i<=n;i++){
		int l=0,r=min(i,n-i),nw=0;
		while(l<=r){
			int mid=l+r>>1;
			if(Hash[0].HSS(i-mid+1,i)==Hash[0].RHSS(i+1,i+mid)){
				nw=mid;
				l=mid+1;
			}else r=mid-1;
		}
		int nl=i-nw,nr=i+nw;
		l=0,r=min(nl,n-nr+1),nw=0;
		while(l<=r){
			int mid=l+r>>1;
			if(Hash[0].HSS(nl-mid+1,nl)==Hash[1].RHSS(nr,nr+mid-1)){
				nw=mid;
				l=mid+1;
			}else r=mid-1;
		}
		ans=max(ans,nw*2+nr-nl);
	}
}
int main(){
	cin>>n;
	Hash[0].read();
	Hash[1].read();
	solve();
	swap(Hash[0].s,Hash[1].s);
	Hash[0].init();Hash[1].init();
	solve();
	cout<<ans;
}
/*
things to check
0.delete cerr code or use '//'
1.initallize(especially multicases)
2.int overflow/long long mle
3.if make the ans is hard , try 2-divided
4.memory &b-&a
5.function canshu position
6.the format of input
7.size enough ?
8.the name of function
9.stop copying x0->y0
*/