#include<bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
const ull MAXN = 2e5+10,base = 19260817;
void tomin(int& x,int y){x = min(x,y);} void tomax(int& x,int y){x = max(x,y);}
int n,ans; string s[2]; ull pw[MAXN];

struct DS{
	ull h[MAXN],rh[MAXN];
	void Init(string s){
		s = " " + s;
		for(int i=1;i<=n;i++)h[i] = h[i-1] * base + (s[i] - 'a' + 1);
		for(int i=n;i>=1;i--)rh[i] = rh[i+1] * base + (s[i] - 'a' + 1);
	}
	ull qry(int l,int r,int t = 1){
		if(l>r)return 0;
		int len = r-l+1;
		return (t>0) ? (h[r]-h[l-1]*pw[len]) : (rh[l]-rh[r+1]*pw[len]);	
	}
}t[2];

void calc(){
	t[0].Init(s[0]),t[1].Init(s[1]);

	for(int i=1;i<=n;i++){ //以i为中心
		int L = 1,R = min(i-1,n-i),len = 0;
		while(L<=R){
			int mid = (L+R)>>1;
			if(t[0].qry(i-mid,i-1) == t[0].qry(i+1,i+mid,-1)){len = mid;L = mid+1;}
			else R = mid-1;
		}
		L = 1,R = min(i-len-1,n-(i+len)+1); int w = 0;
		while(L<=R){
			int mid = (L+R)>>1;
			if(t[0].qry(i-len-mid,i-len-1) == t[1].qry(i+len,i+len+mid-1,-1)){w = mid;L = mid+1;}
			else R = mid-1;
		}
		tomax(ans,2*len+1+2*w);
	}
	for(int i=1;i<=n;i++){ //以i-(i+1)中心
		int L = 1,R = min(i,n-i),len = 0;
		while(L<=R){
			int mid = (L+R)>>1;
			if(t[0].qry(i-mid+1,i) == t[0].qry(i+1,i+mid,-1)){len = mid;L = mid+1;}
			else R = mid-1;
		}
		L = 1,R = min(i-len,n-(i+len)+1);int w = 0;
		while(L<=R){
			int mid = (L+R)>>1;
			if(t[0].qry(i-len+1-mid,i-len) == t[1].qry(i+len,i+len+mid-1,-1)){w = mid;L = mid+1;}
			else R = mid-1;
		}
		tomax(ans,2*len+2*w);
	}
}
int main(){
	cin>>n>>s[0]>>s[1];
	pw[0] = 1;for(int i=1;i<=2*n;i++)pw[i] = pw[i-1] * base;
	//	
	calc();
	reverse(s[0].begin(),s[0].end()); reverse(s[1].begin(),s[1].end()); swap(s[0],s[1]);
	calc();
	
	cout<<ans<<endl;
	return 0;
}