组合数 - 题目

#3751. 组合数

统计

给出 $n$ 和 $k$，求 $\min\{\frac{n!}{k! (n - k)!}, 10^{18}\}$ 的值。

其中 $n! = 1 \times 2 \times \cdot \times n$ 表示 $n$ 的阶乘。

输入格式

输入文件包含多组数据，请处理到文件结束。

每组数据包含两个整数 $n$ 和 $k$.

$0 \leq k \leq n \leq 10^9$
至多 $10^5$ 组数据。

输出格式

对于每组数据，输出一个整数，表示所求的值。

样例输入

1000000000 0
1000000000 2
1000000000 500000000

样例输出

1
499999999500000000
1000000000000000000

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