shunfurh
编程介的小学生
2019-01-12 13:01
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从键盘输入一个表达式,计算其中包含的子表达式和操作数的个数,使用C语言求解谢谢大家

Problem Description
YY is a clever boy. One day, he feels very boring and writes some expressions randomly. Later, he discovers that although some expressions were written in different forms, they are essentially the same, such as a+(b-c), (a+b)-c. After several attempts, he becomes interested in this and wants to know the number of distinct expressions involving n different operands.

To make the problem easier, you can assume that only operators +, -, *, / and parentheses are permitted.

Input
The input consists of multiple test cases.

For each test case, there is one line containing only one integer n. (1<=n<=30)
End of input is indicated by a line containing a zero.

Output
For each test case, output the number of distinct expressions involving n different operands. Since the answer is very large, you only need to output the answer modulo 1,000,000,007.

Sample Input
1
2
3
4
0

Sample Output
1
6
68
1170

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