#include<bits/stdc++.h>
using namespace std;

#define int long long
// #define ls p<<1
// #define rs p<<1|1
#define msp(_array) memset(_array,0x3f,sizeof _array)
#define ms0(_array) memset(_array,0,sizeof _array)
#define msn(_array) memset(_array,-1,sizeof _array)
#define mc(_tar,_array) memcpy(_tar,_array,sizeof _tar)
#define pii pair<int,int>
#define endl '\n'

bool bg_memory;
const int mod=1226999999;
const int inf=2147483647;
const int bs=23333;
const double eps=1e-6;
const int N=1e5+7,M=1e5+7;
inline void cmax(int &a,int b){a=a<b?b:a;}
inline void cmin(int &a,int b){a=a>b?b:a;}
inline int qp(int a,int b){int res=1;while(b){if(b&1)res=res*a%mod;a=a*a%mod;b>>=1;}return res;}

int n;
string s,t;
int hs[N],ht[N],rhs[N],rht[N];
int pw[N];
int ans;

mt19937 rnd(time(0));
int Case=1;
void Main(){
    
    cin>>n>>s>>t;
    s=' '+s;
    t=' '+t;
    pw[0]=1;
    for(int i=1;i<=n;i++) pw[i]=pw[i-1]*bs%mod;
    for(int i=1;i<=n;i++) hs[i]=(hs[i-1]*bs%mod+s[i])%mod;
    for(int i=1;i<=n;i++) ht[i]=(ht[i-1]*bs%mod+t[i])%mod;
    for(int i=n;i>=1;i--) rhs[i]=(rhs[i+1]*bs%mod+s[i])%mod;
    for(int i=n;i>=1;i--) rht[i]=(rht[i+1]*bs%mod+t[i])%mod;
    for(int i=1;i<=n;i++){
        int l=1,r=min(i,n-i+1),res=1;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i]-hs[i-mid]*pw[mid]%mod+mod)%mod==(rhs[i]-rhs[i+mid]*pw[mid]%mod+mod)%mod) res=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-res,n-(i+res-1)+1);
        int res2=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i-res]-hs[i-res-mid]*pw[mid]%mod+mod)%mod==(rht[i+res-1]-rht[i+res-1+mid]*pw[mid]%mod+mod)%mod) res2=mid,l=mid+1;
            else r=mid-1;
        }
        cmax(ans,2*res-1+2*res2);
    }
    for(int i=1;i<n;i++){
        int l=0,r=min(i,n-i),res=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i]-hs[i-mid]*pw[mid]%mod+mod)%mod==(rhs[i+1]-rhs[i+mid+1]*pw[mid]%mod+mod)%mod) res=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-res,n-(i+res)+1);
        int res2=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i-res]-hs[i-res-mid]*pw[mid]%mod+mod)%mod==(rht[i+res]-rht[i+res+mid]*pw[mid]%mod+mod)%mod) res2=mid,l=mid+1;
            else r=mid-1;
        }
        cmax(ans,2*res+2*res2);
    }
    for(int i=1;i<=n;i++){
        int l=1,r=min(i,n-i+1),res=1;
        while(l<=r){
            int mid=l+r>>1;
            if((ht[i]-ht[i-mid]*pw[mid]%mod+mod)%mod==(rht[i]-rht[i+mid]*pw[mid]%mod+mod)%mod) res=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-res+1,n-(i+res-1));
        int res2=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i-res+1]-hs[i-res+1-mid]*pw[mid]%mod+mod)%mod==(rht[i+res]-rht[i+res+mid]*pw[mid]%mod+mod)%mod) res2=mid,l=mid+1;
            else r=mid-1;
        }
        cmax(ans,2*res-1+2*res2);
    }
    for(int i=1;i<n;i++){
        int l=0,r=min(i,n-i),res=0;
        while(l<=r){
            int mid=l+r>>1;
            if((ht[i]-ht[i-mid]*pw[mid]%mod+mod)%mod==(rht[i+1]-rht[i+1+mid]*pw[mid]%mod+mod)%mod) res=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-res+1,n-(i+res));
        int res2=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i-res+1]-hs[i-res+1-mid]*pw[mid]%mod+mod)%mod==(rht[i+res+1]-rht[i+res+mid+1]*pw[mid]%mod+mod)%mod) res2=mid,l=mid+1;
            else r=mid-1;
        }
        cmax(ans,2*res+2*res2);
    }
    for(int i=1;i<=n;i++){
        int l=1,r=min(i,n-i+1),res=0;
        while(l<=r){
            int mid=l+r>>1;
            if((hs[i]-hs[i-mid]*pw[mid]%mod+mod)%mod==(rht[i]-rht[i+mid]*pw[mid]%mod+mod)%mod) res=mid,l=mid+1;
            else r=mid-1;
        }
        cmax(ans,2*res);
    }
    cout<<ans<<endl;

    return;
}
string RdFile="c";
bool en_memory;

signed main(){
    auto bg_clock=chrono::high_resolution_clock::now();
#ifdef ONLINE_JUDGE
    // freopen((RdFile+".in").c_str(),"r",stdin);
    // freopen((RdFile+".out").c_str(),"w",stdout);
#endif
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    // cin>>Case;
    while(Case--) Main();
    auto en_clock=chrono::high_resolution_clock::now();
    auto duration_clock=chrono::duration_cast<chrono::microseconds>(en_clock-bg_clock);
#ifndef ONLINE_JUDGE
    cerr<<endl<<"code_time_used: "<<duration_clock.count()*0.001<<"ms"<<endl;
    cerr<<"code_memory_used: "<<(&en_memory-&bg_memory)/1024.0/1024<<"MB"<<endl;
#endif
    return 0;
}