#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    double k;
    string a, b;
    cin >> k >> a >> b;

    int n = 0;
    for(int i = 0; i <a.size(); i++)
        if(a[i] == b[i]) n++;

    if(n  * 1.0 / a.size() >= k) cout << "yes";
    else cout << "no";

    return 0;
}