Coin change

Time limit2sMemory limit512 MB

Summary

Find the fewest 2 won and 5 won coins that sum to n, or report -1 when no combination works.

Level: Easy3 of 10
Topics: Greedy, Math, Brute force
Solved: No attempts yet

Problem

Chunhyang works at the counter of a convenience store.

A customer asks for change in 2 won coins and 5 won coins only. Both kinds of coins are available without limit. The change has to be paid with as few coins as possible. Given the amount of change $n$ , write a program that reports the minimum number of coins.

For example, change of 15 won is paid with three 5 won coins, so 3 coins in total. Change of 14 won is paid with two 5 won coins and two 2 won coins, so 4 coins. Change of 13 won is paid with one 5 won coin and four 2 won coins, so 5 coins.

Input

The first line contains the amount of change $n$ ( $1 \le n \le 100000$ ).

Output

Print the minimum number of coins on the first line. If the amount cannot be paid with 2 won and 5 won coins, print -1.

Examples2

Example 1
Input
```
13
```
Expected output
```
5
```
Example 2
Input
```
14
```
Expected output
```
4
```