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