import java.io.*; import java.util.*; import java.text.*; import java.math.*; import java.util.regex.*; public class Solution { public static void main(String[] args) { Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] a = new int[n]; for(int a_i=0; a_i < n; a_i++){ a[a_i] = in.nextInt(); } int compteur = 0; int i; for (i = 0; i < a.length; i++){ for(int j = i+1; j < a.length; j++){ if (Math.abs(a[i] - a[j]) <= 1){ compteur++; break; } } } System.out.println(compteur); } }