## Description:

0xfaner just learned the factorial today, and the factorial is defined as follows:

$$
x!=1 \times 2 \times \dots \times x
$$

He found that $$$ 10!=3628800 $$$ ， $$$ 20!=2432902008176640000 $$$ ,the number of trailing zeros is increasing.

Now 0xfaner wants to know the the number of trailing zeros of $$$ n! $$$ to each given $$$ n $$$ .

## Input:

The only line contains one integer $$$ n $$$ ( $$$ 1 \leq n \leq 10^9 $$$ ).

## Output:

Print the number of trailing zeros of $$$ n! $$$ .

## Sample Input:

25

## Sample Output:

6