Minimum number of bills

Given positive integer N (8 ≤ N ≤ 1000000), which defines any integer amount of money ≤ 1000000. It is known that the integer sum of money greater than or equal to 7 monetary units, can be requested only bills in denominations of 2 and 5 monetary units. Determine how many denominations of 2 and 5 units of money can give the amount of N units of money to their total number was minimal.

Input

Single number - the sum given.

Output

Single number - the required minimum number of cuts.

Examples