#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
int main()
{
double k,cnt;
string a,b;
cin>>k>>a>>b;
for(int i=0;i<a.size();i++)
if(a[i]==b[i]) cnt++;
if(cnt/a.size()>=k)
cout<<"yes";
else
cout<<"no";
return 0;
}