public class JR2 {

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] arr = new int[n];
        for(int i = 0; i < n; i++){
            arr[i] = in.nextInt();
        }
        System.out.println(solution(arr));
    }

    public static int solution(int[] arr) {
        mergeSort(arr, 0, arr.length - 1);
        int count = 0;
        int flag = 1;
        for (int i = 0; i < arr.length - 1; i++) {
            if (Math.abs(arr[i] - arr[i + 1]) <= 10) {
                if (flag == 3) {
                    flag = 1;
                } else {
                    flag += 1;
                }
            } else {
                if (flag == 3) {
                    flag = 1;
                } else {
                    count += 3 - flag;
                    flag = 1;
                }
            }
        }
        if (flag!=3){
            count+=3-flag;
        }
        return count;
    }

   
    public static void merge(int[] arr, int low, int mid, int height) {
        int i = low;
        int j = mid + 1;
        int k = 0;
        int[] temp = new int[height - low + 1];
        while (i <= mid && j <= height) {
            if (arr[i] <= arr[j]) {
                temp[k++] = arr[i++];
            } else {
                temp[k++] = arr[j++];
            }
        }

        while (i <= mid) {
            temp[k++] = arr[i++];
        }

        while (j <= height) {
            temp[k++] = arr[j++];
        }

        for (int m = 0; m < temp.length; m++) {
            arr[low + m] = temp[m];
        }
    }


    public static void mergeSort(int[] arr, int low, int height) {
        if (low < height) {
            int mid = (low + height) / 2;
            mergeSort(arr, low, mid);
            mergeSort(arr, mid + 1, height);
            merge(arr, low, mid, height);
        }
    }
}