#include<bits/stdc++.h>

using namespace std;
using E=long long;
constexpr E mod=1e9+7,BS=131;

struct stringHash{
  vector<E> c,pw;
  stringHash(){ };
  stringHash(string str){
    pw=c=vector<E>(str.size());
    pw[0]=1;
    for(int i=1; i<str.size(); i++){
      c[i]=(c[i-1]*BS+str[i]-'a')%mod;
      pw[i]=pw[i-1]*BS%mod;
    }
  }

  E get(int l,int r){
    return (c[r]-c[l-1]*pw[r-l+1]%mod+mod)%mod;
  }
};

int main(){

  int n;
  cin>>n;
  string S1,S2;
  cin>>S1>>S2;
  S1=" "+S1;
  S2=" "+S2;

  stringHash hs1(S1),hs2(S2);
  reverse(S1.begin()+1,S1.end());
  reverse(S2.begin()+1,S2.end());
  stringHash ihs1(S1),ihs2(S2);

  int ans=1;
  int j=1;
  for(int i=1; i<=n; i++){
    while(j<i&&hs1.get(j,i)!=ihs1.get(n-i+1,n-j+1)) j++;
    ans=max(ans,i-j+1);
    j=max(j-2,1);
  }
  j=1;
  for(int i=1; i<=n; i++){
    while(j<i&&hs2.get(j,i)!=ihs2.get(n-i+1,n-j+1)) j++;
    ans=max(ans,i-j+1);
    j=max(j-2,1);
  }

  auto chk1=[&](int x)->bool{
    int len=(x-1)*2+1;
    for(int i=x; i<=n; i++){
      int l=0,r=min(i-1,n-i);
      while(l<r){
        int mid=(l+r+1)>>1;
        if(hs1.get(i-mid,i+mid)==ihs1.get(n-(i+mid)+1,n-(i-mid)+1)) l=mid;
        else r=mid-1;
      }
      int mid=l;
      if(mid+1>=x) return 1;
      if(hs2.get(i+mid,i+mid+(len-x-mid)-1)==ihs1.get(n-(i-x+1+len-x-mid-1)+1,n-(i-x+1)+1)) return 1;
    }
    for(int i=n-x+1; i; i--){
      int l=0,r=min(i-1,n-i);
      while(l<r){
        int mid=(l+r+1)>>1;
        if(hs2.get(i-mid,i+mid)==ihs2.get(n-(i+mid)+1,n-(i-mid)+1)) l=mid;
        else r=mid-1;
      }
      int mid=l;
      if(mid+1>=x) return 1;
      if(ihs1.get(n-(i-mid)+1,n-(i-mid-(len-x-mid)+1)+1)==hs2.get(i+x-1-(len-x-mid)+1,i+x-1)) return 1;
    }
    return 0;
  };

  auto chk2=[&](int x)->bool{
    int len=x*2;
    for(int i=x; i<=n; i++){
      int l=0,r=min(i,n-i);
      while(l<r){
        int mid=(l+r+1)>>1;
        if(hs1.get(i-mid+1,i+mid)==ihs1.get(n-(i+mid)+1,n-(i-mid+1)+1)) l=mid;
        else r=mid-1;
      }
      int mid=l;
      if(mid>=x) return 1;
      if(hs2.get(i+mid,i+mid+(len-x-mid)-1)==ihs1.get(n-(i-x+1+len-x-mid-1)+1,n-(i-x+1)+1)) return 1;
    }
    for(int i=n-x+1; i; i--){
      int l=0,r=min(i-1,n-i+1);
      while(l<r){
        int mid=(l+r+1)>>1;
        if(hs2.get(i-mid,i+mid-1)==ihs2.get(n-(i+mid-1)+1,n-(i-mid)+1)) l=mid;
        else r=mid-1;
      }
      int mid=l;
      if(mid>=x) return 1;
      if(ihs1.get(n-(i-mid)+1,n-(i-mid-(len-x-mid)+1)+1)==hs2.get(i+x-1-(len-x-mid)+1,i+x-1)) return 1;
    }
    return 0;
  };

  int l=1,r=n;
  while(l<r){
    int mid=(l+r+1)>>1;
    if(chk1(mid+1)) l=mid;
    else r=mid-1;
  }
  ans=max(ans,l*2+1);

  l=1,r=n;
  while(l<r){
    int mid=(l+r+1)>>1;
    //cerr<<l<<' '<<r<<' '<<mid<<' '<<chk2(mid)<<endl;
    if(chk2(mid)) l=mid;
    else r=mid-1;
  }
  ans=max(ans,l*2);

  cout<<ans<<endl;

  return 0;
}