import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        int sum = a[0];
        for (int i = n - 1; i > 0; i--) {
            if (a[i - 1] != a[i] - 1)
                sum += a[i];
        }
        System.out.println(sum);
    }
}