#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ri register
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
const int inf=0x3f3f3f3f;
inline int rd(){
	int x=0,y=1;char c=getchar();
	for(;c<'0'||c>'9';c=getchar())if(c=='-')y=-1;
	for(;c>='0'&&c<='9';c=getchar())x=(x<<1)+(x<<3)+(c^48);
	return x*y;
}
const int N=1e5+5,B=1e4+7;
int n,ans;
char a[N],b[N];
unsigned long long pra[N],prb[N],pw[N],sufa[N],sufb[N];
unsigned long long cpre(unsigned long long pre[],int l,int r){
	return pre[r]-pre[l-1]*pw[r-l+1];
}
unsigned long long csuf(unsigned long long suf[],int l,int r){
	return suf[l]-suf[r+1]*pw[r-l+1]; 
}
int calc(int l,int r){
	int L=0,R=min(l-1,n-r+1),ans=0;
	while(L<=R){
		int mid=L+R>>1;
		if(cpre(pra,l-mid,l-1)==csuf(sufb,r,r+mid-1))ans=mid,L=mid+1;
		else R=mid-1;
	}
	return ans;
}
int calc2(int l,int r){
	int L=1,R=min(l,n-r),ans=0;
	while(L<=R){
		int mid=L+R>>1;
		if(cpre(pra,l-mid+1,l)==csuf(sufb,r+1,r+mid))ans=mid,L=mid+1;
		else R=mid-1;
	}
	return ans;
}
signed main(){
	n=rd();scanf("%s%s",a+1,b+1);
	for(int i=1;i<=n;i++)
		pra[i]=pra[i-1]*B+a[i],
		prb[i]=prb[i-1]*B+b[i];
	for(int i=n;i;i--)
		sufa[i]=sufa[i+1]*B+a[i],
		sufb[i]=sufb[i+1]*B+b[i];
	pw[0]=1;for(int i=1;i<=n;i++)pw[i]=pw[i-1]*B;
	for(int i=1;i<=n;i++){
		int l=1,r=min(i-1,n-i),res=0;
		while(l<=r){
			int mid=l+r>>1;
			if(cpre(pra,i-mid,i-1)==csuf(sufa,i+1,i+mid))res=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,1+res*2+calc(i-res,i+res)*2);
		l=1;r=min(i,n-i);res=0;
		while(l<=r){
			int mid=l+r>>1;
			if(cpre(pra,i-mid+1,i)==csuf(sufa,i+1,i+mid))res=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,res*2+calc(i-res+1,i+res)*2);
	}
	for(int i=1;i<=n;i++){
		int l=1,r=min(i-1,n-i),res=0;
		while(l<=r){
			int mid=l+r>>1;
			if(cpre(prb,i-mid,i-1)==csuf(sufb,i+1,i+mid))res=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,1+res*2+calc2(i-res,i+res)*2);
		l=1;r=min(i,n-i);res=0;
		while(l<=r){
			int mid=l+r>>1;
			if(cpre(prb,i-mid+1,i)==csuf(sufb,i+1,i+mid))res=mid,l=mid+1;
			else r=mid-1;
		}
		ans=max(ans,res*2+calc2(i-res+1,i+res)*2);
	}
	cout<<ans<<'\n';
	return 0;
}