#include<bits/stdc++.h>
#define int long long
#define db double
#define maxn 1000005
#define mod 1000000007
#define fir first
#define sec second
#define pr pair<int,int>
#define mk make_pair
#define inf 10000000000000000
using namespace std;
inline int read()
{
    int SS=0,WW=1;
    char ch=getchar();
    while(ch<'0'||ch>'9')
	{
        if(ch=='-')WW=-1;
        ch = getchar();
    }
    while(ch>='0'&&ch<='9')
	{
        SS=(SS<<1)+(SS<<3)+(ch^48);
        ch=getchar();
    }
    return SS*WW;
}
inline void write(int XX)
{
    if(XX<0)putchar('-'),XX=-XX;
    if(XX>9)write(XX/10);
    putchar(XX% 10 + '0');
}
int n,ans,pl[maxn],pw[maxn],hs1[maxn],hs2[maxn],bs=233;
char a[maxn],b[maxn];
void solve(string x,string y) 
{
	pw[0]=1,hs1[0]=x[0];
	for(int i=1;i<=n;i++)pw[i]=pw[i-1]*bs,pl[i]=0;
	for(int i=1;i<=n+1;i++)hs1[i]=hs1[i-1]*bs+x[i];
	for(int i=n+1;i;i--)hs2[i]=hs2[i+1]*bs+y[i];
	for(int i=1,mid=0,r=0;i<=n;i++)
	{
		if(i<=r)pl[i]=min(pl[mid*2-i],r-i+1);
		while(x[i-pl[i]]==x[i+pl[i]])pl[i]++;
		if(i+pl[i]>r)r=i+pl[i]-1,mid=i;
	}
	for(int i=1;i<=n;i++)
	{
		int p=max(ans,pl[i]);
		for(;p<=i;p++)
			if(hs1[i-pl[i]]-hs1[i-p-1]*pw[p-pl[i]+1]!=hs2[i+pl[i]-2]-hs2[i+p-1]*pw[p-pl[i]+1])
				break;
		ans=max(ans,p);
	}
}
signed main()
{
	n=read(),a[0]=b[0]='~',a[2*n+1]=b[2*n+1]='|';
	for(int i=1;i<=n;i++)cin>>a[i*2],a[i*2-1]='|';
	for(int i=1;i<=n;i++)cin>>b[i*2],b[i*2-1]='|';
	n*=2,solve(a,b),reverse(a+2,a+n+1),reverse(b+2,b+n+1),solve(b,a);
	write(ans-1);
	return 0;
}