#include<bits/stdc++.h>
using namespace std;
const int N=4e5+10,B='六';
typedef unsigned long long ULL;
char S[N],T[N];
char s[N];
ULL p[N],h[N];
int n;

int P(int i,int t)
{
	if(t&1) return i+(t-1)*n;
	else return n-i+1+(t-1)*n;
}

ULL get(int l,int r)
{
	return h[r]-h[l-1]*p[r-l+1];
}

int Lcp(int i,int j,int mx)
{
	if(mx<0) return -N;
	int l=1,r=mx,ans=0;
	while(l<=r)
	{
		int mid=l+r>>1;
		if(get(i,i+mid-1)==get(j,j+mid-1)) ans=mid,l=mid+1;
		else r=mid-1;
	}
	return ans;
}

signed main()
{
	// freopen(".in","r",stdin);
	// freopen(".out","w",stdout);

	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);

	cin>>n;
	p[0]=1;
	for(int i=1;i<=n*4;i++) p[i]=p[i-1]*B;
	cin>>(S+1);
	cin>>(T+1);

	for(int i=1;i<=n;i++) s[i]=S[i],s[i+n]=S[n-i+1],s[i+n*2]=T[i],s[i+n*3]=T[n-i+1];

	for(int i=1;i<=n*4;i++) h[i]=h[i-1]*B+s[i];

	int ans=0;
	//at point
	for(int i=1,x,l,r,mx,c,len;i<=n;i++)
	{
		x=Lcp(P(i,2),P(i,1),min(i,n-i+1)),len=x*2-1;
		l=i-x,r=i+x;
		c=Lcp(P(l,2),P(r-1,3),min(l,n-r+2));
		ans=max(ans,len+c*2);

		x=Lcp(P(i,4),P(i,3),min(i,n-i+1)),len=x*2-1;
		l=i-x,r=i+x;
		c=Lcp(P(l+1,2),P(r,3),min(l+1,n-r+1));
		ans=max(ans,len+c*2);
	}
	//at edge
	for(int i=1,x,l,r,mx,c,len;i<n;i++)
	{
		x=Lcp(P(i,2),P(i+1,1),min(i,n-i)),len=x*2;
		l=i-x,r=i+1+x;
		c=Lcp(P(l,2),P(r-1,3),min(l,n-r+2));
		ans=max(ans,len+c*2);

		x=Lcp(P(i,4),P(i+1,3),min(i,n-i)),len=x*2;
		l=i-x,r=i+1+x;
		c=Lcp(P(l+1,2),P(r,3),min(l+1,n-r+1));
		ans=max(ans,len+c*2);
	}

	cout<<ans<<"\n";

	return 0;
}