include [HTML_REMOVED]

using namespace std;
int main()
{

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

}