// Arup Guha
// 6/3/2013
// Solution to 2013 KTH Challenge Problem H: FreeCell

import java.util.*;

public class freecell {

	public static int n;
	public static int[] memo;

	public static void main(String[] args) {

		// Get input.
		Scanner stdin = new Scanner(System.in);
		n = stdin.nextInt();
		int numFree = stdin.nextInt();
		int k = stdin.nextInt();

		// Get max result for n and m.
		memo = new int[numFree+1];
		Arrays.fill(memo, -1);
		int max = go(numFree);

		// Ta da!
		if (k <= max)
			System.out.println("yes");
		else
			System.out.println("no");
	}

	public static int go(int numFree) {

		// Put n in free cells, 1 to final pile...
		if (numFree == 0) return n+1;

		// First we form a solution for nF-1, then nF-2, ... to 0.
		int res = 0;
		for (int i=0; i<numFree; i++)
			res += go(i);

		// Ta da!
		return memo[numFree] = res + (n+1);
	}
}