MAY99_4 - Rachu


Rachu is very happy today beacause its his birthday :D and he has a bday party at home with 'r' friends.

He went to market to purchase something to eat .(He is really fond of eating :P ).

At the shop he found muffins at a very reasonable price (ohh!! he loves muffins ;) ).

He bought 'n' muffins from the shop.

After reaching home he is wondering that in how many ways  he can distribute these muffins between his friends .

He shouldn't be rash so he would give atleast 1 muffin to each friend.

For rest of the muffins left he can distribute it in any manner. He is still wondering the no. of ways in which he can distribute these muffins.

Help him out by writing a code which calculates the no. of ways the muffins could be distributed and print "-1" (quotes for clarity) if its impossible for him to distribute the muffins.  

 Consider each muffin as similar. The no. of ways could go very large so output the reult after taking a mod with 10000007 .

Input

The input consists of 2 integers :
  n : The no. of muffins
  r : The no. of friends

Output

The required answer modulo 10000007

Constraints

1<= n,r <= 100

Example

Input:
2 1

Output:
1
Input:
4 2

Output:

3

Explanation

In 1st case he has 2 muffins and called only 1 friend so he gave both the muffins to him .

In 2nd case he 1st give 1 muffin each to both.
Then he can give 0 muffin to 1st friend and 2 to the 2nd or 1 muffin to each or 2 muffins to 1st friend and 0 to the 2nd.

 


hide comments
viratian_070: 2017-07-01 06:42:53

easy stuff...but remember printing "-1"

heisenberg0820: 2017-06-22 15:19:02

100th :)

sas1905: 2017-05-23 17:12:25

when n<r print -1 not zero costed me two WA's..hardly 5-6 lines in python..

.::Austin::.: 2016-07-10 23:16:04

IIT JEE mathematics :D

Piyush Kumar: 2016-06-12 14:16:51

This is not DP, this is basic Combinatorics, and the with the given constraints, it is too easy in python!

Arjav Patel: 2016-01-16 16:28:07

Easy one with dp!

RADHE SHYAM LODHI: 2015-08-29 09:28:11

green after 1 RE, 4WA, 3TLE :D

Last edit: 2015-08-29 09:28:28
Bhuvnesh Jain: 2015-07-16 21:19:28

constraints were too less to learn something at all.... atleast n, r should be about 10^5 and time limit more struct as there is only one test only in each file..... if constraints not changed.... problems should be moved to tutorials.....

mrx: 2015-07-11 14:19:46

lol no such big things required, just see the pattern which you obtain.

Shashank Tiwari: 2015-07-06 19:19:16

1) 10000007 = 941*10627 ; where 941 , 10627 are prime.
2) Also Phi(10000007) = 9988440
3) Euler's theorem
4) a/b is congruent to a*b^ ( phi(k-1) ) modulo k if gcd(b,k) =1
5) If n<r don't forget to print -1.


Added by:Mayank Tuteja
Date:2013-01-18
Time limit:0.179s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
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Resource:Gunjit Agrawal