#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector> 
#define int long long
using namespace std;

const int md=998244353,bas=131;
void read(int &x){
	x=0;
	char c=getchar();
	while(!('0'<=c && c<='9')){
		c=getchar();
	}
	while('0'<=c && c<='9'){
		x=(x<<3)+(x<<1)+(c^48);
		c=getchar();
	}
}
int n,pw[600010],hsh[600010];
char s[600010];
int gethsh(int l,int r){
	if(l>r){
		return 0;
	}
	return (hsh[r]+(md-pw[r-l+1])*hsh[l-1])%md;
}
int getlcp(int i,int j,int upl){
	//printf("[LCP %lld %lld %lld]:",i,j,upl);
	int ql=0,qr=upl+1;
	while(ql<qr-1){
		int mid=(ql+qr)>>1;
		if(gethsh(i,i+mid-1)==gethsh(j,j+mid-1)){
			ql=mid;
		}else{
			qr=mid;
		}
	}
	//printf("[%lld]\n",ql);
	return ql;
}
int getlcs(int i,int j,int upl){
	//printf("[LCS %lld %lld %lld]:",i,j,upl);
	int ql=0,qr=upl+1;
	while(ql<qr-1){
		int mid=(ql+qr)>>1;
		if(gethsh(i-mid+1,i)==gethsh(j-mid+1,j)){
			ql=mid;
		}else{
			qr=mid;
		}
	}
	//printf("[%lld]\n",ql);
	return ql;
}
signed main(){
	pw[0]=1;
	for(int i=1;i<=400005;i++){
		pw[i]=pw[i-1]*bas%md;
	} 
	read(n);
	n++;
	scanf(" %s %s",s+1,s+n+2);
	s[n+1]='#';
	for(int i=1;i<=2*n;i++){
		hsh[i]=(hsh[i-1]*bas+s[i])%md;
	}
	//printf("[%lld %lld]",gethsh(1,3),gethsh(10,12));
	int res=0;
	for(int i=1;i<=n/2;i++){
		for(int j=i;j+i<=n;j+=i){
			int cl=getlcs(j,j+i,i),cr=getlcp(j+1,j+i+1,min(i-cl,n-j-i));
			if(j+2*i-cl>n){
				continue;
			} 
			if(cl+cr==i || gethsh(j+cr+1,j+i-cl)==gethsh(n+j+cr+1+i,n+j+i+i-cl)){
				res=i;
				break;
			}
		}
		if(res==i){
			continue;
		}
		for(int j=i;j+i<=n;j+=i){
			int cl=getlcs(n+j,n+j+i,i),cr=getlcp(n+j+1,n+j+i+1,min(i-cl,n-j-i));
			if(cl+cr==i || gethsh(j+cr-i+1,j-cl)==gethsh(n+j+cr+1,n+j+i-cl)){
				res=i;
				break;
			}
		}
		if(res==i){
			continue;
		}
		for(int j=i;j+i<=n;j+=i){
			int cl=getlcs(j,n+j+i,i),cr=getlcp(j+1,n+j+i+1,min(i-cl,n-j-i));
			if(cl+cr==i || gethsh(j+cr-i+1,j-cl)==gethsh(j+cr+1,j+i-cl)){
				res=i;
				break;
			}
			if(j+2*i-cl<=n && gethsh(n+j+cr+1,n+j+i-cl)==gethsh(n+j+cr+1+i,n+j+i+i-cl)){
				continue;
			} 
			
		}
	}
	printf("%lld",res*2);
	return 0;
}
/*
5
abcab
acabc
*/