#include <iostream>
#include <cstring>

using namespace std;

int main()
{
    double x;
    cin >> x;

    string a,b;
    cin >> a >> b;

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

    double y = static_cast<double>(sum) / a.size();

    if (y>=x) cout << "yes" << endl;
    else cout << "no" << endl;

    return 0;
}