#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ull unsigned long long
const int N=1e5+5;
int n,res;
ull q1[N],q2[N],h1[N],h2[N],pw[N];
string s1,s2;
ull gq1(int l,int r){
	return q1[r]-q1[l-1]*pw[r-l+1];
}
ull gh1(int l,int r){
	return h1[l]-h1[r+1]*pw[r-l+1];
}
ull gq2(int l,int r){
	return q2[r]-q2[l-1]*pw[r-l+1];
}
ull gh2(int l,int r){
	return h2[l]-h2[r+1]*pw[r-l+1];
}
signed main(){
	cin>>n>>s1>>s2;
	pw[0]=1;
	for(int i=1;i<=n;i++)q1[i]=q1[i-1]*131+s1[i-1],q2[i]=q2[i-1]*131+s2[i-1],pw[i]=pw[i-1]*131;
	for(int i=n;i>=1;i--)h1[i]=h1[i+1]*131+s1[i-1],h2[i]=h2[i+1]*131+s2[i-1];
	for(int i=1;i<=n;i++){
		int l=1,r=min(i,n-i+1);
		while(l<r){
			int mid=l+r+1>>1;
			if(gq1(i,i+mid-1)==gh1(i-mid+1,i))l=mid;
			else r=mid-1;
		}	
		res=max(res,2*l-1);
		int L=l,R=min(i,n-i+2);
		while(L<R){
			int mid=L+R+1>>1;
			if(gq2(i+l-1,i+mid-2)==gh1(i-mid+1,i-l))L=mid;
			else R=mid-1;
		}
		res=max(res,2*L-1);
		l=1,r=min(i,n-i+1);
		while(l<r){
			int mid=l+r+1>>1;
			if(gq2(i,i+mid-1)==gh2(i-mid+1,i))l=mid;
			else r=mid-1;
		}
		res=max(res,2*l-1);
		L=l,R=min(n-i+1,i+1);
		while(L<R){
			int mid=L+R+1>>1;
			if(gq2(i+l,i+mid-1)==gh1(i-mid+2,i-l+1))L=mid;
			else R=mid-1;
		}
		res=max(res,2*L-1);
		l=0,r=min(i,n-i);
		while(l<r){
			int mid=l+r+1>>1;
			if(gq1(i+1,i+mid)==gh1(i-mid+1,i))l=mid;
			else r=mid-1;
		}
		res=max(res,2*l);
		L=l,R=min(i,n-i+1);
		while(L<R){
			int mid=L+R+1>>1;
			if(gq2(i+l,i+mid-1)==gh1(i-mid+1,i-l))L=mid;
			else R=mid-1;
		}
		res=max(res,2*L);
		l=0,r=min(i,n-i);
		while(l<r){
			int mid=l+r+1>>1;
			if(gq2(i+1,i+mid)==gh2(i-mid+1,i))l=mid;
			else r=mid-1;
		}
		res=max(res,2*l);
		L=l,R=min(n-i,i+1);
		while(L<R){
			int mid=L+R+1>>1;
			if(gq2(i+l+1,i+mid)==gh1(i-mid+2,i-l+1))L=mid;
			else R=mid-1;
		}
		res=max(res,2*L);
	}
	cout<<res;
}