#include <iostream>
#include <cstring>
using namespace std;
 
int main() {
	char a[100001], b[100001]; 
	int l1, l2, l, k = 0;
	cin >> a >> b >> l;
	l1 = strlen(a);
	l2 = strlen(b);
	if (l1 < l || l2 < l) cout << "NO";
	else {
		for (int i = 0; i < l1; i ++) {
			for (int j = i; j <= l ; j ++) {
				if (a[j] == b[j]) k ++;
				else i++;
				if (k == l) {
					cout << "YES";
					return 0;
				}
			}
			k = 0;
		}
		cout << "NO";
	}
	return 0;
}