#include<bits/stdc++.h>
using namespace std;
const int MAX=1e5+10;
int n,ans,l,r,x;string s[2];
#define ull unsigned long long
ull p[MAX],ha[MAX][2],ha1[MAX][2];
const ull P=1e9+7;
inline int read(){
	int x=0,f=1;char c=getchar();
	while(c>'9'||c<'0'){if(c=='-')f=-1;c=getchar();}
	while(c<='9'&&c>='0'){x=(x<<3)+(x<<1)+(c^48);c=getchar();}
	return x*f;
}
inline ull ask(int l,int r,int x){
	return ha[r][x]-ha[l-1][x]*p[r-l+1];
}inline ull ask1(int l,int r,int x){
	return ha1[l][x]-ha1[r+1][x]*p[r-l+1];
}
signed main(){
	n=read();cin>>s[0]>>s[1];p[0]=1;
	for(int i=1;i<=n;++i){
        // cout<<i<<endl;
		for(int j=0;j<=1;++j)
			ha[i][j]=ha[i-1][j]*P+s[j][i-1];
		p[i]=p[i-1]*P;
	}
	for(int i=n;i;--i)
		for(int j=0;j<=1;++j)
			ha1[i][j]=ha1[i+1][j]*P+s[j][i-1];
	ans=1;
	for(int i=1;i<=n;++i){
        // cout<<i<<" "<<x<<endl;
		l=1,r=min(i,n-i+1),x=1;
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-mid+1,i,0)==ask1(i,i+mid-1,0)){
				x=mid;l=mid+1;
			}else  r=mid-1;
		}l=0,r=min(i-x,n-(i+x-1)+1);
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-x-mid+1,i-x,0)==ask1(i+x-1,i+x-1+mid-1,1)){
				ans=max(ans,(x+mid<<1)-1);l=mid+1;
			}else  r=mid-1;
		}
		l=1,r=min(i,n-i),x=0;
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-mid+1,i,0)==ask1(i+1,i+mid,0)){
				x=mid;l=mid+1;
			}else  r=mid-1;
		}l=0,r=min(i-x,n-(i+x)+1);
                // cout<<i<<" "<<x<<" "<<r<<endl;
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-x-mid+1,i-x,0)==ask1(i+x,i+x+mid-1,1)){
				ans=max(ans,(x+mid<<1));l=mid+1;
			}else  r=mid-1;
		}
	}
	//------
	//     ---
	for(int i=1;i<=n;++i){
		l=1,r=min(i,n-i+1),x=1;
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-mid+1,i,1)==ask1(i,i+mid-1,1)){
				x=mid;l=mid+1;
			}else  r=mid-1;
		}l=0,r=min(i-x,n-(i+x-1)+1);
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-x+1-mid+1,i-x+1,0)==ask1(i+x,i+x+mid-1,1)){
				ans=max(ans,(x+mid<<1)-1);l=mid+1;
			}else  r=mid-1;
		}
		l=1,r=min(i,n-i),x=0;
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-mid+1,i,1)==ask1(i+1,i+mid,1)){
				x=mid;l=mid+1;
			}else  r=mid-1;
		}l=0,r=min(i-x,n-(i+x)+1);
		while(l<=r){
			int mid=l+r>>1;
			if(ask(i-x+1-mid+1,i-x+1,0)==ask1(i+x+1,i+x+1+mid-1,1)){
				ans=max(ans,(x+mid<<1));l=mid+1;
			}else  r=mid-1;
		}
	}
	//---
	//  ------
	printf("%d",ans);
}