Valid Array

An integer array is valid if it contains five elements that become five consecutive integers after sorting. In other words, among those five selected values, every adjacent difference after sorting is 1.

For example, the array {6, 1, 9, 5, 7, 15, 8} is valid because it contains 5, 6, 7, 8, 9.

Given an array, determine the minimum number of new elements that must be added so that the array becomes valid.

The first line contains N, the size of the array. N is a positive integer at most 50. Each of the next N lines contains one element of the array. Each element is a nonnegative integer at most 1,000,000,000, and no two elements are equal.

Print the minimum number of elements that must be added so that the given array becomes valid.