/*
 *                                                     __----~~~~~~~~~~~------___
 *                                    .  .   ~~//====......          __--~ ~~
 *                    -.            \_|//     |||\\  ~~~~~~::::... /~
 *                 ___-==_       _-~o~  \/    |||  \\            _/~~-
 *         __---~~~.==~||\=_    -_--~/_-~|-   |\\   \\        _/~
 *     _-~~     .=~    |  \\-_    '-~7  /-   /  ||    \      /
 *   .~       .~       |   \\ -_    /  /-   /   ||      \   /
 *  /  ____  /         |     \\ ~-_/  /|- _/   .||       \ /
 *  |~~    ~~|--~~~~--_ \     ~==-/   | \~--===~~        .\
 *           '         ~-|      /|    |-~\~~       __--~~
 *                       |-~~-_/ |    |   ~\_   _-~            /\
 *                            /  \     \__   \/~                \__
 *                        _--~ _/ | .-~~____--~-/                  ~~==.
 *                       ((->/~   '.|||' -_|    ~~-/ ,              . _||
 *                                  -_     ~\      ~~---l__i__i__i--~~_/
 *                                  _-~-__   ~)  \--______________--~~
 *                                //.-~~~-~_--~- |-------~~~~~~~~
 *                                       //.-~~~--\
 *                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *                               神兽保佑            永无BUG
 */

/*
 * @Description: I want to be the weakest vegetable in the world!
 * @Author: I.Z.
 */
#include<bits/stdc++.h>
using namespace std;
#define MOD         998244353
#define speMOD      2933256077ll
#define pii         pair<int,int>
#define all(v)      v.begin(),v.end()
#define pb          push_back
#define REP(i,b,e)  for(int i=(b);i<(int)(e);++i)
#define over(x)     {cout<<(x)<<endl;return;}
#define lowbit(x)   ((x)&(-(x)))
#define cntbit(x)   __builtin_popcount(x)
#define rf(v)       shuffle(all(v),sd);
#define deal(v)     sort(all(v));v.erase(unique(v.begin(),v.end()),v.end())
#define lbound(v,x) lower_bound(all(v),x)-v.begin()
mt19937 sd(random_device{}());
int qpow(int a,int b,int m=MOD,int res=1){
	a%=m;
	while(b>0)res=(b&1)?(res*a%m):(res),a=a*a%m,b>>=1;
	return res;
}
string YN(bool x,string Y="Yes",string N="No") {
	if(x){
		return Y;
	} else {
		return N;
	}
}
int exgcd(int x,int y,int &a,int &b){
	if(y==0){
		a=1;b=0;
		return x;
	}
	int d=exgcd(y,x%y,a,b);
	int z=b;
	b=a-b*(x/y);
	a=z;
	return d;
}
int _x_,_y_;
inline int inverse(int x,int y=MOD){
	exgcd(x,y,_x_,_y_);
	return (_x_+y)%y;
}
int fac[2000005],inv[2000005];
void init(int n){
	fac[0]=inv[0]=1;
	REP(i,1,n+1)fac[i]=fac[i-1]*i%MOD;
	inv[n]=qpow(fac[n],MOD-2);
	for(int i=n-1;i>=1;--i)inv[i]=inv[i+1]*(i+1)%MOD;
}
int binom(int x,int y){
	return x<y||y<0? 0:fac[x]*inv[y]%MOD*inv[x-y]%MOD;
}
int sa[400005],rk[400005],ht[400005],st[400005][20],cnt[400005],id[400005],old[400005];
bool same(int x,int y,int w,int n){return x+w<n&&y+w<n&&old[x]==old[y]&&old[x+w]==old[y+w];}
int query(int l,int r){
	if(rk[l]>rk[r])swap(l,r);
	l=rk[l]+1;r=rk[r];
	int s=__lg(r-l+1);
	return min(st[l][s],st[r-(1<<s)+1][s]);
}
void buildsa(string s){
	int n=s.size(),m=200;
	REP(i,0,m)cnt[i]=0;
	REP(i,0,n)++cnt[rk[i]=s[i]];
	REP(i,1,m)cnt[i]+=cnt[i-1];
	REP(i,0,n)sa[--cnt[rk[i]]]=i;
	for(int w=1;w<n;w<<=1){
		int cur=0;
		for(int i=n-1;i>=n-w;--i)id[cur++]=i;
		REP(i,0,n)if(sa[i]>=w)id[cur++]=sa[i]-w;
		REP(i,0,m)cnt[i]=0;
		REP(i,0,n)old[i]=rk[i],++cnt[rk[id[i]]];
		REP(i,1,m)cnt[i]+=cnt[i-1];
		for(int i=n-1;i>=0;--i)sa[--cnt[rk[id[i]]]]=id[i];
		cur=1;rk[sa[0]]=0;
		REP(i,1,n)if(same(sa[i],sa[i-1],w,n))rk[sa[i]]=cur-1;else rk[sa[i]]=cur++;
		if(cur==n)break;else m=cur;
	}
	int k=0;
	REP(i,0,n)if(rk[i]){
		int t=sa[rk[i]-1];k=max(k-1,0);
		while(i+k<n&&t+k<n&&s[i+k]==s[t+k])++k;
		ht[rk[i]]=k;
	}
	REP(i,0,n)st[i][0]=ht[i];
	REP(j,0,__lg(n)){
		REP(i,0,n-(1<<(j+1))+1)st[i][j+1]=min(st[i][j],st[i+(1<<j)][j]);
	}
}
int n,m;
string s1,s2;
int Id(int x,int y){return (x==1? y:(x==2? y+n+1:(x==3? m+n+2-y-1:m*2+3-y-1)));}
int qr(int x,int y,int z,int w){return query(Id(x,y),Id(z,w));}
void Main() {
	cin>>n>>s1>>s2;
	string s3=s1,s4=s2;
	reverse(all(s3));reverse(all(s4));
	buildsa(s1+'#'+s2+'%'+s3+'$'+s4);
	int ans=0;m=n*2;
	REP(i,0,n)ans=max(ans,qr(1,i,3,i)*2-1);
	REP(i,0,n)ans=max(ans,qr(2,i,4,i)*2-1);
	REP(i,0,n-1)ans=max(ans,qr(1,i+1,3,i)*2);
	REP(i,0,n-1)ans=max(ans,qr(2,i+1,4,i)*2);
	REP(i,0,n)ans=max(ans,qr(3,i,2,i)*2);
	REP(i,0,n){
		int x=qr(1,i,3,i);
		if(x<=i&&i+x-1<n)ans=max(ans,qr(3,i-x,2,i+x-1)*2+x*2-1);
	}
//	cout<<ans<<endl;
	REP(i,0,n){
		int x=qr(2,i,4,i);
		if(i-x+1>=0&&i+x<n)ans=max(ans,qr(3,i-x+1,2,i+x)*2+x*2-1);
	}
//	cout<<ans<<endl;
	REP(i,1,n){
		int x=qr(1,i,3,i-1);
		if(i-x-1>=0&&i+x-1<n)ans=max(ans,qr(3,i-x-1,2,i+x-1)*2+x*2);
	}
	REP(i,1,n){
		int x=qr(2,i,4,i-1);
		if(i-x>=0&&i+x<n)ans=max(ans,qr(3,i-x,2,i+x)*2+x*2);
	}
	cout<<ans<<endl;
}
void TC() {
    int tc=1;
	while(tc--){
		Main();
		cout.flush();
	}
}
signed main() {
	return cin.tie(0),cout.tie(0),ios::sync_with_stdio(0),TC(),0;
}
/*
1. CLEAR the arrays (ESPECIALLY multitests)
2. DELETE useless output
 */