#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
string s1,s2;
int main()
{
	int i,l;double s,n;
	cin>>n>>s1>>s2;
	l=s1.size();
	for(i=1;i<=l-1;i++)
	{
		if(s1[i]==s2[i])s++;
	}
	s=1/s;
	if(s<n)
		cout<<"no"; 
	else
		cout<<"yes";
	return 0;
}