#include<bits/stdc++.h>
#define il inline
#define all(x)    (x).begin(),(x).end()
#define mem(x,y)  memset((x),(y),sizeof((x)))
#define input(x)  freopen(x,"r",stdin)
#define output(x) freopen(x,"w",stdout)
using namespace std;
using db=double;
using ll=long long;
using ull=unsigned long long;
const int N=1e5+10;
const ll  mod=10000000000001743ll,base=100000471;
using i64=__int128;
i64 p[N];
struct hash
{
    i64 h1[N],h2[N];
    il void solve(char* s)
    {
        mem(h1,0),mem(h2,0);int n=strlen(s+1);
        for(int i=1;i<=n;++i) h1[i]=(h1[i-1]*base+s[i])%mod;
        for(int i=n;i>=1;--i) h2[i]=(h2[i+1]*base+s[i])%mod;
    }
    il i64 gh1(int l,int r){return ((h1[r]-h1[l-1]*p[r-l+1])%mod+mod)%mod;}
    il i64 gh2(int l,int r){return ((h2[l]-h2[r+1]*p[r-l+1])%mod+mod)%mod;}
}h1,h2;
il int solve(int n,char *s1,char *s2)
{
    int ans=0;
    h1.solve(s1),h2.solve(s2);
    for(int i=1;i<=n;++i)
    {
        int ans1=0;
        for(int L=1,R=min(i-1,n-i),mid=L+R>>1;L<=R;mid=L+R>>1)
        {
            int l=i-mid,r=i+mid;
            if(h1.gh1(l,r)==h1.gh2(l,r)) L=mid+1,ans1=mid;
            else R=mid-1;
        }
        int p1=i-ans1-1,p2=i+ans1,ans2=0;
        for(int L=0,R=min(p1,n-p2+1),mid=L+R>>1;L<=R;mid=L+R>>1)
        {
            if(h1.gh2(p1-mid+1,p1)==h2.gh1(p2,p2+mid-1)) L=mid+1,ans2=mid;
            else R=mid-1;
        }
        ans=max(ans,2*ans1+2*ans2+1);
    }
    for(int i=1;i<=n;++i)
    {
        int ans1=-1;
        for(int L=0,R=min(i-1,n-i-1),mid=L+R>>1;L<=R;mid=L+R>>1)
        {
            int l=i-mid,r=i+1+mid;
            if(h1.gh1(l,r)==h1.gh2(l,r)) L=mid+1,ans1=mid;
            else R=mid-1;
        }
        int p1=i-ans1-1,p2=i+1+ans1,ans2=0;
        for(int L=0,R=min(p1,n-p2+1),mid=L+R>>1;L<=R;mid=L+R>>1)
        {
            if(h1.gh2(p1-mid+1,p1)==h2.gh1(p2,p2+mid-1)) L=mid+1,ans2=mid;
            else R=mid-1;
        }
        ans=max(ans,2*ans1+2*ans2+2);
    }
    return ans;
}
char s1[N],s2[N];
int main()
{
    p[0]=1;for(int i=1;i<N;++i)p[i]=p[i-1]*base%mod;
    ios::sync_with_stdio(false);
    cin.tie(nullptr);cout.tie(nullptr);
    int n,ans=0;
    cin>>n>>s1+1>>s2+1;
    ans=solve(n,s1,s2);
    reverse(s1+1,s1+n+1),reverse(s2+1,s2+n+1);
    ans=max(ans,solve(n,s2,s1));
    cout<<ans;
    return 0;
}