Binomial Coefficient
Compute C(N, R), the number of ways to choose R from N.
Input format
One line with two integers N and R (0 <= R <= N <= 30).
Output format
Print the binomial coefficient C(N, R), the number of ways to choose R items from N.
Constraints
- Values fit in a 64-bit signed integer
- Trailing whitespace and a trailing newline are ignored by the judge
Read from stdin, write to stdout. Sample cases below show the exact format.
Sample cases
Example 1
Input
5 2Expected output
10Example 2
Input
6 3Expected output
20