Compute N! (High Precision Required)

Problem Background

Special for beginners, ^_^

Problem Description

Using a recursive algorithm, compute the exact value of $N!$ ($N$ is input as an ordinary integer).

Input Format

One integer $N\ (1 \le N \le 40)$.

Output Format

Output the result of $N!$, formatted as in the sample, with no spaces in the middle.

Sample Input

10

Sample Output

10!=3628800

Constraints

1s, 1024KiB for each test case.