package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	if !scanner.Scan() {
		return
	}
	n, _ := strconv.Atoi(scanner.Text())
	counts := make([]int, 150002)
	for i := 0; i < n; i++ {
		scanner.Scan()
		w, _ := strconv.Atoi(scanner.Text())
		counts[w]++
	}

	ans := 0
	lastUsed := 0
	for w := 1; w <= 150000; w++ {
		for counts[w] > 0 {
			if w-1 > lastUsed && w-1 >= 1 {
				lastUsed = w - 1
				ans++
				counts[w]--
			} else if w > lastUsed {
				lastUsed = w
				ans++
				counts[w]--
			} else if w+1 > lastUsed {
				lastUsed = w + 1
				ans++
				counts[w]--
			} else {
				break
			}
		}
	}
	fmt.Println(ans)
}