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