#include <iostream>
using namespace std;
int main()
{
float k;
int cnt =0;
cin >> k;
string a,b;
cin >> a >> b;
for(int i =0;a[i];i++) if(a[i]==b[i]) cnt+=1;
if((float)cnt/a.size() >= k) cout << "yes" << endl;
else cout << "no" << endl;
return 0;
}