#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<cmath> 
#include<string>
using namespace std;
int main(){
	double d;
	cin >> d;
	string s1,s2;
	int z;
	cin >> s1;
	cin >> s2;
	z = s1.length();
	int cnt=0;
	for(int i=0;i<z;i++){
		if(s1[i] == s2[i]){
			cnt++;
		}
	}
	double res;
	res = cnt*1.0/z;
	if(res >= d){
		cout << "yes";
	}else{
		cout << "no";
	}
	return 0;
}