#include<iostream>
#include<vector>
#include<atcoder/modint>
#include<cassert>
using namespace std;
using mint=atcoder::modint998244353;
int N;
string U,V;
mint ans;
mint p2[2<<17];
vector<mint>calc(string u,int idx)
{
	vector<mint>A;
	for(int i=u.size();i>idx;i--)
	{
		if(A.empty())A.push_back(p2[N-i+1]-1);
		else A.push_back(p2[N-i]);
	}
	return A;
}
main()
{
	cin>>N>>U>>V;
	p2[0]=1;
	for(int i=1;i<=N;i++)p2[i]=p2[i-1]+p2[i-1];
	for(int i=1;i<N;i++)ans+=p2[i]*(p2[N-i]-1)*(p2[N]-p2[N-i]);
	if(U==V)
	{
		cout<<ans.val()<<endl;
		return 0;
	}
	int idx=0;
	while(idx<U.size()&&idx<V.size()&&U[idx]==V[idx])idx++;
	vector<mint>A=calc(U,idx),B=calc(V,idx);
	if(A.empty()||B.empty())
	{
		A.push_back(p2[N]-1-(p2[N-idx+1]-1)+1);
		A.back()+=p2[N-idx]-1;
	}
	else
	{
		A.push_back(p2[N]-1-(p2[N-idx+1]-1)+1);
	}
	while(!B.empty())
	{
		A.push_back(B.back());
		B.pop_back();
	}
	mint s=0;
	for(mint a:A)s+=a;
	assert(s==p2[N]-1);
	vector<mint>SA1(A.size()),SA2(A.size());
	for(int j=A.size();j--;)
	{
		if(j+1<A.size())SA1[j]=SA1[j+1],SA2[j]=SA2[j+1];
		SA1[j]+=((int)A.size()-2*j)*A[j];
		SA2[j]+=A[j];
	}
	for(int i=0;i<A.size();i++)
	{
		int lj=i+A.size()/2+1;
		if(lj<A.size())
		{
			ans+=A[i]*(SA1[lj]+SA2[lj]*2*i);
		}
	}
	cout<<ans.val()<<endl;
}