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A - A Recursive Function

Score : $100$ points

Problem Statement

A function $f(x)$ defined for non-negative integer $x$ satisfies the following conditions:

• $f(0) = 1$;
• $f(k) = k \times f(k-1)$ for all positive integers $k$.

Find $f(N)$.

Constraints

• $N$ is an integer such that $0 \le N \le 10$.

Input

The input is given from Standard Input in the following format:

$N$

Output

Print the answer as an integer.

2

2

We have $f(2) = 2 \times f(1) = 2 \times 1 \times f(0) = 2 \times 1 \times 1 = 2$.

3

6

We have $f(3) = 3 \times f(2) = 3 \times 2 = 6$.

0

1

10

3628800