#include <bits/stdc++.h>
using namespace std;
int main()
{
double k,t=0;
string s1,s2;
cin>>k>>s1>>s2;
for(int i=0;i<s1.size();i++)
{
if(s1[i]==s2[i]) t++;
}
if((t/s1.size())>=k) cout<<"yes";
else cout<<"no";
return 0;
}