#include<bits/stdc++.h>
using namespace std;
mt19937_64 rnd(random_device{}());
const int mod=998244353;
int base;
int n,ans,rd[127];
string s1,s2;
struct hsh{
	int pw[200005],pre[200005],suc[200005];
	void init(string s)
	{
		pw[0]=1;
		for(int i=1;i<=n;i++)
		{
			pw[i]=1ll*pw[i-1]*base%mod;
		}
		for(int i=1;i<=n;i++)
		{
			pre[i]=(1ll*pre[i-1]*base+rd[s[i]])%mod;
		}
		for(int i=n;i>=1;i--)
		{
			suc[i]=(1ll*suc[i+1]*base+rd[s[i]])%mod;
		}
	}
	int get1(int l,int r)
	{
		return ((pre[r]-1ll*pre[l-1]*pw[r-l+1]%mod)+mod)%mod;
	}
	int get2(int l,int r)
	{
		return ((suc[l]-1ll*suc[r+1]*pw[r-l+1]%mod)+mod)%mod;
	}
}H1,H2;
void solve(string s1,string s2)
{
	s1=" "+s1;
	s2=" "+s2; 
	H1.init(s1);
	H2.init(s2);
	for(int i=1;i<=n;i++)
	{
		int l=0,r=min(i-1,n-i);
		while(l<r)
		{
			int mid=(l+r+1)>>1;
			if(H1.get1(i-mid,i-1)==H1.get2(i+1,i+mid)) l=mid;
			else r=mid-1;
		}
		int pl=i-l-1,pr=i+l;
		int L=0,R=min(pl,n-pr+1);
		while(L<R)
		{
			int mid=(L+R+1)>>1;
			if(H1.get1(pl-mid+1,pl)==H2.get2(pr,pr+mid-1)) L=mid;
			else R=mid-1;
		}
		if(pl-L>=1&&pr+L<=n&&s1[pl-L]==s2[pr+L]) throw ;
		ans=max(ans,(l+L)*2+1);
		l=0,r=min(i,n-i);
		while(l<r)
		{
			int mid=(l+r+1)>>1;
			if(H1.get1(i-mid+1,i)==H1.get2(i+1,i+mid)) l=mid;
			else r=mid-1;
		}
		pl=i-l,pr=i+l;
		L=0,R=min(pl,n-pr+1);
		while(L<R)
		{
			int mid=(L+R+1)>>1;
			if(H1.get1(pl-mid+1,pl)==H2.get2(pr,pr+mid-1)) L=mid;
			else R=mid-1;
		}
		ans=max(ans,(l+L)*2);
	}
}
int main()
{
	cin>>n>>s1>>s2;
	base=rnd()%mod;
	for(int i='a';i<='z';i++) rd[i]=rnd()%mod;
	solve(s1,s2);
	reverse(s1.begin(),s1.end());
	reverse(s2.begin(),s2.end());
	solve(s2,s1);
	cout<<ans;
}