//复习完毕
#include <iostream>

using namespace std;

int main()
{
    double k;
    cin >> k;
    string a, b;
    cin >> a >> b;
    double len = 0;
    for (int i = 0; i < a.size(); i ++ )
        if (a[i] == b[i]) len ++ ;

    if (len / a.size() >= k) cout << "yes" << endl;
    else cout << "no" << endl;

    return 0;

}