#include<set>
#include<map>
#include<cmath>
#include<ctime>
#include<stack>
#include<queue>
#include<deque>
#include<string>
#include<bitset>
#include<vector>
#include<cstdio>
#include<random>
#include<complex>
#include<cstdlib>
#include<climits>
#include<iomanip>
#include<cstring>
#include<cassert>
#include<stdlib.h>
#include<iostream>
#include<algorithm>
#include<unordered_map>
using namespace std;
#define getchar()(p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
char buf[1<<21],*p1=buf,*p2=buf;
const long long _base=107374183;
int writetemp[30];
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;
    return x;
}
inline void write(long long x)
{
    int tot=(x==0);
    writetemp[1]=0;
    while(x) writetemp[++tot]=x%10,x/=10;
    while(tot) putchar(writetemp[tot--]+'0');
    putchar('\n');
    return ;
}
const int mod=1000000007,base=31;
int n,ans;
char a[1000010],b[1000010];
long long mul[1000010];
long long haa[1000010],hab[1000010];
long long pd(long long x)
{
    if(x>=mod) return x-mod;
    return x;
}
long long get_a(int l,int r)
{
    return pd(haa[r]-haa[l-1]*mul[r-l+1]%mod+mod);
}
long long get_b(int l,int r)
{
    return pd(hab[r]-hab[l-1]*mul[r-l+1]%mod+mod);
}
int solve(char *a,char *b)
{
    for(int i=1;i<=n;i++) haa[i]=(haa[i-1]*base+a[i]-'a')%mod;
    for(int i=1;i<=n;i++) hab[i]=(hab[i-1]*base+b[i]-'a')%mod;
    for(int k=n;k>=1;k--)
    {
        for(int now=k;now+k-1<=n;now+=k) if(get_a(now-k+1,now)==get_b(now,now+k-1)) return k+k;
        for(int now=k;now+k-1<=n;now+=k)
        {
            int nxt=now+k,nowlen=0;
            int l=0,r=k;
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now-mid+1,now)==get_a(nxt-mid+1,nxt)) l=mid;
                else r=mid-1;
            }
            now++,nxt++,nowlen=l;
            l=0,r=min(k,n-nxt+1);
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now,now+mid-1)==get_a(nxt,nxt+mid-1)) l=mid;
                else r=mid-1;
            }
            now+=l,nxt+=l-1,nowlen+=l;
            l=0,r=min(k,n-nxt+1);
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now,now+mid-1)==get_b(nxt,nxt+mid-1)) l=mid;
                else r=mid-1;
            }
            nowlen+=l;
            if(nowlen>=k) return k+k;
        }
        for(int now=k;now+k-1<=n;now+=k)
        {
            int nxt=now+k,nowlen=0;
            now++;
            int l=0,r=min(k,n-nxt+1);
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now,now+mid-1)==get_b(nxt,nxt+mid-1)) l=mid;
                else r=mid-1;
            }
            now--,nxt--,nowlen=l;
            l=0,r=k;
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now-mid+1,now)==get_b(nxt-mid+1,nxt)) l=mid;
                else r=mid-1;
            }
            now-=l,nxt-=l-1,nowlen+=l;
            l=0,r=min(k,now);
            while(l<r)
            {
                int mid=(l+r+1)>>1;
                if(get_a(now-mid+1,now)==get_a(nxt-mid+1,nxt)) l=mid;
                else r=mid-1;
            }
            nowlen+=l;
            if(nowlen>=k) return k+k;
        }
    }
    return 0;
}
int main()
{
    // freopen("s.out","r",stdin);
    // freopen("a.out","w",stdout);
    scanf("%d",&n),mul[0]=1;
    scanf("%s%s",a+1,b+1);
    for(int i=1;i<=n;i++) mul[i]=mul[i-1]*base%mod;
    ans=solve(a,b);
    for(int i=1;i<=(n>>1);i++) swap(a[i],a[n-i+1]),swap(b[i],b[n-i+1]);
    ans=max(ans,solve(b,a));
    printf("%d\n",ans);
    return 0;
}
/*
6
aaabab
aabbab
*/