#include <bits/stdc++.h>
#define ull unsigned long long
//#define int long long
using namespace std;
const int N = 1e5+5;
const ull P = 131;
int n, m,ans;
char s[N],t[N];
ull p[N];
struct Hsh {
	ull hsh[N],hsh2[N];
	inline void build(char *s) {
		for(int i=1; i<=n; ++i) hsh[i]=hsh[i-1]*P+s[i];
		for(int i=n; i; --i) hsh2[i]=hsh2[i+1]*P+s[i];
	}

	inline ull query(int l,int r,int rev=0) {
		if(rev) return hsh2[l]-hsh2[r+1]*p[r-l+1];
		else return hsh[r]-hsh[l-1]*p[r-l+1];
	}
} Hs,Ht;
int pre[N],suf[N];

inline int Lcp(int L,int R) {
	int l=1,r=min(L,n-R+1),res=0;
	while(l<=r) {
		int mid=l+r>>1;
		if(Hs.query(L-mid+1,L)==Ht.query(R,R+mid-1,1)) res=mid,l=mid+1;
		else r=mid-1;
	}
	return res;
}

inline void solve() {
	Hs.build(s),Ht.build(t);
	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.query(i-mid+1,i)==Hs.query(i,i+mid-1,1)) l=mid+1,res=mid;
			else r=mid-1;
		}
		ans=max(ans,res*2-1+2*Lcp(i-res,i+res-1));
		l=1,r=min(i,n-i),res=0;
		while(l<=r) {
			int mid=l+r>>1;
			if(Hs.query(i-mid+1,i)==Hs.query(i+1,i+mid,1)) l=mid+1,res=mid;
			else r=mid-1;
		}
		ans=max(ans,res*2+2*Lcp(i-res,i+res));
	}
}
signed main() {
	scanf("%d%s%s",&n,s+1,t+1);
	for(int i=p[0]=1; i<N; ++i) p[i]=p[i-1]*P;
	solve();
	for(int i=1; i<=n; ++i) swap(s[i],t[i]);
	for(int i=1; i<=n/2; ++i) swap(s[i],s[n-i+1]),swap(t[i],t[n-i+1]);
	solve();
	cout<<ans<<"\n";
	return 0;
}