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11050번

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import java.util.Scanner;
public class Practice76 {

	static int N, K;
	static int[][] D;
	public static void main(String[] args) throws Exception{
		Scanner sc = new Scanner(System.in);

		N = sc.nextInt();
		K = sc.nextInt();
		
		D = new int[N + 1][N + 1];
		for(int i = 0; i <= N; i++) {
			D[i][1] = i;
			D[i][0] = 1;
			D[i][i] = 1;
		}
		
		for(int i = 2; i <= N; i++) {
			for(int j = 1; j < i; j++) {
				D[i][j] = D[i - 1][j] + D[i - 1][j - 1];
			}
		}
		System.out.println(D[N][K]);
		sc.close();
	}

}