#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#define int long long
using namespace std;
const int MAXN=2e5+10,base=131,mod=1e9+7;
int n,ans,b[MAXN];
struct node
{
    string str,s=" #",t=" #";int a[MAXN],c[MAXN],d[MAXN];
    inline void work()
    {
        str=' '+str;
        for(int i=1;i<=n/2;++i) s+=str[i],s+='#';
        for(int i=n/2;i;--i) t+=str[i],t+='#';
        for(int i=1;i<=n;++i)
            a[i]=(a[i-1]+b[i]*s[i])%mod,
            c[i]=(c[i-1]+b[i]*t[i])%mod;
        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;
                int A=i-mid,B=i,C=i+mid,D=i;
                C=(n+1)-C,D=(n+1)-D;
                int suma=(a[B]-a[A-1]+mod)*b[n-A]%mod;
                int sumb=(c[D]-c[C-1]+mod)*b[n-C]%mod;
                (suma==sumb)?l=mid:r=mid-1;
            }
            d[i]=l,ans=max(ans,d[i]);
        }
    }
}s,t;
inline void work_1()
{
    for(int i=2;i<=n;++i)
    {
        int l=0,r=min(i-1,n-i+2)-s.d[i];
        while(l<r)
        {
            int mid=(l+r+1)>>1;
            int A=i-s.d[i]-mid,B=i-s.d[i]-1,C=i+s.d[i]-2+mid,D=i+s.d[i]-1;
            C=(n+1)-C,D=(n+1)-D;
            int suma=(s.a[B]-s.a[A-1]+mod)*b[n-A]%mod;
            int sumb=(t.c[D]-t.c[C-1]+mod)*b[n-C]%mod;
            (suma==sumb)?l=mid:r=mid-1;
        }
        ans=max(ans,l+s.d[i]);
    }
}
inline void work_2()
{
    for(int i=1;i<n;++i)
    {
        int l=0,r=min(i-1+2,n-i)-t.d[i];
        while(l<r)
        {
            int mid=(l+r+1)>>1;
            int A=i-t.d[i]-mid+2,B=i-t.d[i]+1,C=i+t.d[i]+mid,D=i+t.d[i]+1;
            C=(n+1)-C,D=(n+1)-D;
            int suma=(s.a[B]-s.a[A-1]+mod)*b[n-A]%mod;
            int sumb=(t.c[D]-t.c[C-1]+mod)*b[n-C]%mod;
            (suma==sumb)?l=mid:r=mid-1;
        }
        ans=max(ans,l+t.d[i]);
    }
}
signed main()
{
    cin.tie(0),cout.tie(0);
    ios::sync_with_stdio(0);
    cin>>n>>s.str>>t.str;n=((n<<1)|1),b[0]=1;
    for(int i=1;i<=n;++i) b[i]=b[i-1]*base%mod;
    s.work(),t.work();work_1(),work_2();
    cout<<ans<<'\n';return 0;
}