Fat Cat's cousin II

Source : Unknown
Time limit : 1 sec Memory limit : 32 M

Submitted : 666, Accepted : 296

Fat cat's son is 10 years old now(a small cat? a small mouse? who knows!), and he is doted upon by Fat cat's father-in-law. Oh,do you remember his wife, Mr fat cat is a mordon man and his wife is not a cat but a mouse, a very lovely mouse. Today, fat cat went to see his father-in-law with his family. Grandpa was very happy of course, and as a mathematician he ask his grandson a question: There are n elephants and you seperate them in k groups, how many ways there are will you seperate them? for example there are 4 elephants and you must seperate them in three groups, we name the 4 different elephants 1 2 3 4 and you can seperatet them in the following ways:


{ 1 2 } { 3 } { 4 }            or           { 1 3 } { 2 } { 4 }

{ 1 4 } { 2 } { 3 }            or           { 2 3 } { 1 } { 4 }

{ 2 4 } { 1 } { 3 }            or           { 3 4 } { 1 } { 2 }



there are six way to seperate them

then grandpa ask a lot of questions just the same except n and k are different and grandson answer them all correctly, do you know the answer to the questions?

Input The input will be pairs of integers, one pair per line, and they are all less than 21, the input will end by the end of file.

Sample Input:

4 3
2 2

Output: For each pair of integers, print the number of ways to seperate elephants

Sample output:

6
1

PAT: The order of groups should not be considered.