#include<iostream>
#include<cmath>
#include<string>
#include<cstdio>
#include<cstring>
using namespace std;
int main()
{
	long long n,f=0,i,j,ans=0,x;
	double p;
	string s,t;
	cin>>x>>s>>t;
	n=s.size();
	for(i=0;i<n;i++)
	{
		if(s[i]==t[i])ans++; 
	}
	p=ans*1.0/n;
	if(p>=x)cout<<"yes";
	else cout<<"no";
}