#include<bits/stdc++.h>
using namespace std;
#define ull unsigned long long
#define rep(i,j,k) for(int i=j;i<=k;++i)
#define per(i,j,k) for(int i=j;i>=k;--i)
int const N=2e5+10;
int const B=251;
mt19937_64 rnd(random_device{}());
ull rd[127],hsh1[N],hsh2[N],bse[N];int ans,n;
string s1,s2;
inline ull query1(int l,int r){return hsh1[r]-hsh1[l-1]*bse[r-l+1];}
inline ull query2(int l,int r){return hsh2[r]-hsh2[l-1]*bse[r-l+1];}
#define mid ((l+r)>>1)
inline int lcp1(int x,int y){
	int l=1,r=min(n-x+1,n-y+1),ans=0;
	while (l<=r)
		if (query1(x,x+mid-1)==query1(y,y+mid-1)) l=(ans=mid)+1;
		else r=mid-1;
	return ans;
}
inline int lcs1(int x,int y){
	int l=1,r=min(x,y),ans=0;
	while (l<=r)
		if (query1(x-mid+1,x)==query1(y-mid+1,y)) l=(ans=mid)+1;
		else r=mid-1;
	return ans;
}
inline int lcp(int x,int y){
	int l=1,r=min(n-x+1,n-y+1),ans=0;
	while (l<=r)
		if (query1(x,x+mid-1)==query2(y,y+mid-1)) l=(ans=mid)+1;
		else r=mid-1;
	return ans;
}
inline void work(){
	rep(len,1,(n+1)/2){
		if (2*len<=ans) continue;
		for (int i=1;i+len<=n;i+=len){
			int A=i,B=i+len;
			if (lcp(A,B-1)>=len){ans=max(ans,len*2);break;}
			int sa=lcs1(A,B),sb=lcp1(A,B);
			if (sa+sb-1>=len){ans=max(ans,len*2);break;}
			else{
				int k=lcp(A+sb,B+sb-1);
				if (k+sa+sb-1>=len){ans=max(ans,len*2);break;}
			}
			{
				int sa=lcp1(A+1,B+1);
				if (sa>=len){ans=max(ans,len*2);break;}
				if (lcp(A+sa+1,B+sa)+sa>=len){ans=max(ans,len*2);break;}
			}
		}
	}
}
inline void solve(){
	cin>>n>>s1>>s2,s1=" "+s1,s2=" "+s2;
    if (n==1){
		if (s1[1]==s2[1]) cout<<"2\n";
		else cout<<"0\n";
		return;
	}
	rep(i,'a','z') rd[i]=rnd();
	rep(i,1,n)
		hsh1[i]=(hsh1[i-1]*B+rd[s1[i]]),
		hsh2[i]=(hsh2[i-1]*B+rd[s2[i]]);
	work();
	swap(s1,s2);
	for (int i=1;i<n-i+1;++i) swap(s1[i],s1[n-i+1]),swap(s2[i],s2[n-i+1]);
	rep(i,1,n)
		hsh1[i]=(hsh1[i-1]*B+rd[s1[i]]),
		hsh2[i]=(hsh2[i-1]*B+rd[s2[i]]);
	work();
	cout<<ans<<'\n';
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	bse[0]=1;
	rep(i,1,N-1) bse[i]=bse[i-1]*B;
	int t=1;
	while (t--) solve();
	return 0;
}