#include<bits/stdc++.h>
#define int long long
#define ull unsigned long long
using namespace std;
const int MAXN=2e5+5;
const ull Base=547;
int n;
ull fac[MAXN];
struct String{
    string S;
    ull S1[MAXN],S2[MAXN];
    inline void init(){
        for(int i=1;i<=n;i++)S1[i]=S1[i-1]*Base+(S[i]-'A');
        for(int i=n;i>=1;i--)S2[i]=S2[i+1]*Base+(S[i]-'A');
    }
    inline ull hash1(int l,int r){return S1[r]-S1[l-1]*fac[r-l+1];}
    inline ull hash2(int l,int r){return S2[l]-S2[r+1]*fac[r-l+1];}
    inline bool huiwen(int l,int r){return hash1(l,r)==hash2(l,r);}
}s,t;
inline bool check(int L,int R){
    if(s.S[L]!=t.S[R])return 0;
    int l=1,r=R-L+1;
    while(l<r){
        int mid=l+r+1>>1;
        if(s.hash1(L,L+mid-1)==t.hash2(R-mid+1,R))l=mid;
        else r=mid-1;
    }
    if(l>(R-L+1)/2)return 1;
    return s.huiwen(L+l,R-l+1)||t.huiwen(L+l-1,R-l);
}
inline bool check(int len){
    if(len<=n){
        for(int l=1;l<=n-len+1;l++){
            int r=l+len-1;
            if(s.huiwen(l,r)||t.huiwen(l,r))return 1;
        }
    }
    for(int l=1;l<=n-len+2;l++){
        int r=l+len-2;
        if(check(l,r))return 1;
    }
    return 0;
}
int ans=0;
inline int solve1(){
    int l=0,r=n/2;
    while(l<r){
        int mid=l+r+1>>1;
        if(check(mid<<1|1))l=mid;
        else r=mid-1;
    }
    return l<<1|1;
}
inline int solve2(){
    int l=2,r;
    if((n+1)&1)r=n/2;else r=(n+1)/2;
    while(l<r){
        int mid=l+r+1>>1;
        if(check(mid<<1))l=mid;
        else r=mid-1;
    }
    return l<<1;
}
signed main(){
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);
    cin>>n>>s.S>>t.S;
    s.S=" "+s.S;
    t.S=" "+t.S;
    fac[0]=1;for(int i=1;i<=n;i++)fac[i]=fac[i-1]*Base;
    s.init();t.init();
    ans=max(ans,solve1());
    ans=max(ans,solve2());
    cout<<ans<<"\n";
}