package main

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

func main() {
	reader := bufio.NewReader(os.Stdin)
	var n int
	fmt.Fscan(reader, &n)
	
	var c0, c1, c2 int
	for i := 0; i < n; i++ {
		var a int
		fmt.Fscan(reader, &a)
		rem := a % 3
		if rem == 0 {
			c0++
		} else if rem == 1 {
			c1++
		} else {
			c2++
		}
	}
	
	ans := c0 / 2
	if c1 < c2 {
		ans += c1
	} else {
		ans += c2
	}
	
	fmt.Println(ans)
}