#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
char s1[501],s2[501];
int main()
{ 
    double x,len,k;
    int i;
    cin>>x;
    scanf("%s",s1);
    scanf("%s",s2);
    len=strlen(s1);
    for( i=0;i<len;i++)
    {
    	if(s1[i]==s2[i])
    	{
    		k++;
		}
	}
	if(double(k)/len>=x)
	{
		cout<<"yes";
	}
	else
	{
		cout<<"no";
	}
}