spoj#EXPR3. Counting Expressions
Counting Expressions
Count the number of distinct expressions involving n different operands a, b, c, etc. Only operators +, -, *, / and parentheses are permitted. Single minus operator (for ex. -a*b) is not allowed.
Two expression are distinct if for some valid input values (i.e. You won't divide some number by zero) a, b, c, ... , the two expressions leads to different results. For example, a/b/c and a/(b*c) are the same expressions, but a/b+c and a/(b+c) are not.
Input
Multiply test cases. For each test case:
A single line - n.(1<= n <=50).
Input terminates by a single zero.
Output
For each test case:
The number of different expressions, modulo 499999999999993.
Example
Input: 3 0</p>Output: 68
If you find the constraints is too small in this problem, try problem EXPR4.