#include<bits/stdc++.h>
using namespace std;
#define ull unsigned long long
const int N=1e5+10;
const ull H=31;
int n;char s[N],t[N];
ull hs[N],hs1[N],hs2[N],ht1[N],ht2[N];
bool pd(int op1,int l1,int r1,int op2,int l2,int r2){
	ull h1,h2;
	if(op1==1)h1=hs1[r1]-hs1[l1-1]*hs[r1-l1+1];
	else h1=ht1[r1]-ht1[l1-1]*hs[r1-l1+1];
	if(op2==1)h2=hs2[l2]-hs2[r2+1]*hs[r2-l2+1];
	else h2=ht2[l2]-ht2[r2+1]*hs[r2-l2+1];
	// cout<<"pd:"<<op1<<" "<<l1<<" "<<r1<<"   "<<op2<<" "<<l2<<' '<<r2<<"   "<<(h1==h2)<<endl;
	return h1==h2;
}
signed main(){
	scanf("%d%s%s",&n,s+1,t+1);
	hs[0]=1;for(int i=1;i<=n;i++)hs[i]=hs[i-1]*H;
	for(int i=1;i<=n;i++){
		hs1[i]=hs1[i-1]*H+s[i]-'a'+1;
		ht1[i]=ht1[i-1]*H+t[i]-'a'+1;
	}
	// cout<<"hs1: ";for(int i=1;i<=n;i++)cout<<hs1[i]<<" ";cout<<endl;
	for(int i=n;i>=1;i--){
		hs2[i]=hs2[i+1]*H+s[i]-'a'+1;
		ht2[i]=ht2[i+1]*H+t[i]-'a'+1;
	}
	// cout<<"hs2: ";for(int i=1;i<=n;i++)cout<<hs2[i]<<" ";cout<<endl;
	int ans=0;
	for(int i=1;i<=n;i++){
		int d=0;
		for(int j=18;j>=0;j--){
			int mid=d+(1<<j);
			if(i-mid<1||i+mid>n)continue;
			if(pd(1,i-mid,i-1,1,i+1,i+mid))d=mid;
		}
		ans=max(ans,d*2+1);
		int d2=0;
		for(int j=18;j>=0;j--){
			int mid=d2+(1<<j);
			if(i-d-mid<1||i+d+mid-1>n)continue;
			if(pd(1,i-d-mid,i-d-1,2,i+d,i+d+mid-1))
				d2=mid;
		}
		ans=max(ans,(d+d2)*2+1);
		int d3=0;
		for(int j=18;j>=0;j--){
			int mid=d3+(1<<j);
			if(i-mid<1||i+mid>n)continue;
			if(pd(2,i-mid,i-1,2,i+1,i+mid))d3=mid;
		}
		ans=max(ans,d3*2+1);
		int d4=0;
		for(int j=18;j>=0;j--){
			int mid=d4+(1<<j);
			if(i-d3-mid<1||i+d3+mid-1>n)continue;
			if(pd(1,i-d3-mid+1,i-d3,2,i+d3+1,i+d3+mid))
				d4=mid;
		}
		ans=max(ans,(d3+d4)*2+1);
		int d5=-1;
		for(int j=18;j>=0;j--){
			int mid=d5+(1<<j);
			if(i-mid<1||i+mid>n)continue;
			if(pd(1,i-mid,i,2,i,i+mid))d5=mid;
		}
		ans=max(ans,d5*2+2);
		// cout<<i<<" "<<d<<" "<<d2<<" "<<d3<<" "<<d4<<" "<<d5<<endl;
	}
	for(int i=1;i<n;i++){
		int d=-1;
		for(int j=18;j>=0;j--){
			int mid=d+(1<<j);
			if(i-mid<1||i+mid+1>n)continue;
			if(pd(1,i-mid,i,1,i+1,i+1+mid))d=mid;
		}
		ans=max(ans,d*2+2);
		int d2=0;
		for(int j=18;j>=0;j--){
			int mid=d2+(1<<j);
			if(i-d-mid<1||i+d+mid>n)continue;
			if(pd(1,i-d-mid,i-d-1,2,i+d+1,i+d+mid))
				d2=mid;
		}
		ans=max(ans,(d+d2)*2+2);
		int d3=-1;
		for(int j=18;j>=0;j--){
			int mid=d3+(1<<j);
			if(i-mid<1||i+mid+1>n)continue;
			if(pd(2,i-mid,i,2,i+1,i+1+mid))d3=mid;
		}
		ans=max(ans,d3*2+2);
		int d4=0;
		for(int j=18;j>=0;j--){
			int mid=d4+(1<<j);
			if(i-d3-mid<1||i+d3+mid-1>n)continue;
			if(pd(1,i-d3-mid+1,i-d3,2,i+d3+2,i+1+d3+mid))
				d4=mid;
		}
		ans=max(ans,(d3+d4)*2+2);
		// cout<<i<<" "<<d<<" "<<d2<<" "<<d3<<" "<<d4<<endl;
	}
	cout<<ans<<endl;
	return 0;
}
/*
g++ 3.cpp -o 3 -std=c++14 -O2 -Wall 
./3
*/