#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using u64=unsigned long long;
//using lll=__int128_t;
using lf=long double;
using Pr=pair<int,int>;
#define F(i,l,r) for(ll i=l;i<=ll(r);++i)
#define G(i,r,l) for(ll i=r;i>=ll(l);--i)
#define ct const
#define il inline
#define pb push_back
#define fi first
#define se second
#define mkr make_pair
template<class T>
il void tomn(T&x,T ct&y){y<x?x=y,0:0;}
template<class T>
il void tomx(T&x,T ct&y){x<y?x=y,0:0;}
#define dbg(...) fprintf(stderr,__VA_ARGS__)
#define CUT dbg("===================\n")
ct lf EPS=1e-10L;
il int dcmp(lf x){return fabs(x)<=EPS?0:(x<0?-1:1);}
ct ll INF=4e18L;
//ct int INF=1.02e9;
//il void rd(int&x){scanf("%d",&x);}
//il void rd(ll&x){scanf("%lld",&x);}

void add2(ll ct&P,ll&x,ll y){x+=y,x-=((-(x>=P))&P);}
void sub2(ll ct&P,ll&x,ll y){x-=y,x+=((-(x<0))&P);}
ll add(ll ct&P,ll x,ll y){return add2(P,x,y),x;}
ll sub(ll ct&P,ll x,ll y){return sub2(P,x,y),x;}

ct int N=5.01e5;

void Manacher(int n,char*s,int*r){
	int j=0;
	F(i,1,n){
		if(i<=j+r[j])r[i]=max(0ll,min(j+r[j]-i,(ll)r[2*j-i]));
		while(i+r[i]+1<=n&&i-r[i]-1>=1&&s[i+r[i]+1]==s[i-r[i]-1])++r[i];
		if(i+r[i]>j+r[j])j=i;
	}
}

struct Num{
	static ct ll P=998244353,Q=991145149;
	ll x,y;
	Num operator+(Num a)ct{return Num{add(P,x,a.x),add(Q,y,a.y)};}
	Num operator-(Num a)ct{return Num{sub(P,x,a.x),sub(Q,y,a.y)};}
	Num operator*(Num a)ct{return Num{x*a.x%P,y*a.y%Q};}
	bool operator==(Num a)ct{return a.x==x&&a.y==y;}
	bool operator!=(Num a)ct{return !(*this==a);}
};
ct Num SD{114514,1919810};
Num spw[N];
class Hsh{
	int n;Num d[N];
public:
	void build(int n_,char*s){
		n=n_,d[0]=Num{};
		F(i,1,n)d[i]=d[i-1]*SD+Num{s[i],s[i]};
	}
	Num qry(int l,int r){return d[r]-d[l-1]*spw[r-l+1];}
}hsh[2];

struct Initer{
	Initer(){
		spw[0]=Num{1,1};
		F(i,1,N-1)spw[i]=spw[i-1]*SD;
	}
}initer;

int n,r[N];
char s[2][N];
int qry(int i,int j){
	int len=0;
	G(k,20,0){
		len+=1<<k;
		if(len>i||j+len-1>n||hsh[0].qry(n-i+1,n-i+len)!=hsh[1].qry(j,j+len-1))
			len-=1<<k;
	}
//	dbg("qry(%d, %d) = %d\n",i,j,len);
	return len;
}
int main(){
#ifdef LOCAL
	freopen("A.in","r",stdin);
//	freopen(".out","w",stdout);
#endif
	scanf("%d",&n);
	F(i,0,1)scanf("%s",s[i]+1);
	reverse(s[0]+1,s[0]+n+1);
	hsh[0].build(n,s[0]),hsh[1].build(n,s[1]);
	reverse(s[0]+1,s[0]+n+1);
	int ans=0;
	F(i,1,n)tomx(ans,2*qry(i,i));
	{
		memset(r,0,sizeof(r));
		char*t=s[0];
		t[2*n+3]='+';
		G(i,n,1)t[2*i+2]='#',t[2*i+1]=t[i];
		t[2]='#',t[1]='-';
		Manacher(2*n+3,t,r);
		F(i,2,2*n+1){
			int s=i/2-r[i]/2,t=i/2+(r[i]-1)/2;
			dbg("s[0]: [%d, %d]\n",s,t);
			tomx(ans,r[i]+2*qry(s-1,t));
		}
	}{
		memset(r,0,sizeof(r));
		char*t=s[1];
		t[2*n+3]='+';
		G(i,n,1)t[2*i+2]='#',t[2*i+1]=t[i];
		t[2]='#',t[1]='-';
		Manacher(2*n+3,t,r);
		F(i,2,2*n+1){
			int s=i/2-r[i]/2,t=i/2+(r[i]-1)/2;
			dbg("s[1]: [%d, %d]\n",s,t);
			tomx(ans,r[i]+2*qry(s,t+1));
		}
	}
	printf("%d\n",ans);
}