bool M1;
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define ull unsigned long long
#define LL __int128
#define db double
#define LD long double
#define Pii pair<int,int>
#define Pll pair<ll,ll>
#define Pull pair<ull,ull>
#define Pdb pair<db,db>
#define fir first
#define sec second
#define vec vector<int>
#define pb push_back
#define qlr cerr<<"qlr\n"
#define dyh cerr<<"dyh\n"
#define pc(x) __builtin_popcount(x)
#define uni(x,y) uniform_int_distribution<int>(x,y)(rng)
#define unl(x,y) uniform_int_distribution<ll>(x,y)(rng)
#define unr(x,y) uniform_real_distribution<double>(x,y)(rng)
#define F(i,a,b) for(int i=a,i##end=b;i<=i##end;i++)
#define UF(i,a,b) for(int i=a,i##end=b;i>=i##end;i--)
#define look_memory cerr<<'\n'<<abs(&M1-&M2)/1024.0/1024<<'\n'
#define look_time cerr<<'\n'<<clock()*1.0/CLOCKS_PER_SEC<<'\n'
mt19937 rng(time(0)^(*new int));
const ll INF=0x3f3f3f3f3f3f3f3f;
const int Mod=1e9+7;
template<typename T>
inline void inc(T &a,T b){
	if(b<0) b+=Mod;
	a+=b;
	if(a>=Mod) a-=Mod;
}
template<typename T>
inline void dec(T &a,T b){
	if(b<0) b+=Mod;
	a-=b;
	if(a<0) a+=Mod;
}
template<typename T>
inline void muc(T &a,T b){
	a=a*b%Mod;
}
template<typename T>
inline bool chkmin(T &a,T b){
	if(a<=b) return false;
	a=b;
	return true;
}
template<typename T>
inline bool chkmax(T &a,T b){
	if(a>=b) return false;
	a=b;
	return true;
}
const int base=131;
int n,ans;
char a[100010],b[100010],s1[200010],s2[200010];
int lp1[200010],lp2[200010];
ull pw[100010],h1[100010],h2[100010];
void mnc(int n,char *s,int *lp){
	for(int i=1,mid=0,r=0;i<=n;i++){
		if(i<=r) lp[i]=min(lp[2*mid-i],r-i+1);
		while(s[i-lp[i]]==s[i+lp[i]]) lp[i]++;
		if(chkmax(r,i+lp[i]-1)) mid=i;
	}
}
bool chk(int a,int b,int c,int d){
	if(a<1||b>n||c<1||d>n||a>b||c>d) return 0;
	c=n-c+1,d=n-d+1,swap(c,d);
	return (h1[b]-h1[a-1])*pw[a]==(h2[d]-h2[c-1])*pw[c];
}
int get(int x,int y){
	if(x<1||x>n||y<1||y>n) return 0;
	int L=1,R=min(x,n-y+1),mid;
	while(L<=R){
		mid=(L+R)>>1;
		if(chk(x-mid+1,x,y,y+mid-1)) L=mid+1;
		else R=mid-1;
	}
	return R;
}
void init(){
	#define N 100000
	pw[0]=1;
	F(i,1,N) pw[i]=pw[i-1]*base;
	#undef N
}
bool M2;
int main(){
	// freopen("trade.in","r",stdin);
	// freopen("trade.out","w",stdout);
	srand(time(0)^(*new int));
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	init();
	cin>>n;
	cin>>(a+1);
	cin>>(b+1);

	// n=3;
	// F(i,1,n) a[i]=uni(0,25)+'a';
	// F(i,1,n) b[i]=uni(0,25)+'a';
	// cerr<<(a+1)<<'\n';
	// cerr<<(b+1)<<'\n';

	F(i,1,n) h1[i]=h1[i-1]+a[i]*pw[n-i];
	F(i,1,n) h2[i]=h2[i-1]+b[n-i+1]*pw[n-i];

	F(i,1,n) s1[i*2-1]='#',s1[i*2]=a[i];
	s1[2*n+1]='#',s1[0]='~';
	mnc(2*n+1,s1,lp1);
	F(i,1,n) s2[i*2-1]='#',s2[i*2]=b[i];
	s2[2*n+1]='#',s2[0]='~';
	mnc(2*n+1,s2,lp2);
	
	F(i,1,2*n+1) chkmax(ans,lp1[i]-1);
	F(i,1,2*n+1) chkmax(ans,lp2[i]-1);

	F(i,2,2*n){
		int l=(i-lp1[i])/2+1,r=(i+lp1[i])/2-1;
		chkmax(ans,lp1[i]-1+2*get(l-1,r));
	}
	F(i,2,2*n){
		int l=(i-lp2[i])/2+1,r=(i+lp2[i])/2-1;
		chkmax(ans,lp2[i]-1+2*get(l,r+1));
	}
	cout<<ans;
	look_memory;
	look_time;
	return 0;
}
/*
g++ A1.cpp -o A1 -std=c++14 -O2 -Wall -Wextra -fno-ms-extensions&&./A1

3
wkz
fea

6
bbacdg
efabba
*/