```go
package main

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

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func main() {
	in := bufio.NewReaderSize(os.Stdin, 1<<20)
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	var t int
	fmt.Fscan(in, &t)
	for ; t > 0; t-- {
		var n int
		fmt.Fscan(in, &n)
		cnt := [3]int{}
		for i := 0; i < n; i++ {
			var x int
			fmt.Fscan(in, &x)
			cnt[x%3]++
		}
		ans := cnt[0] + min(cnt[1], cnt[2]) + (cnt[1]-min(cnt[1], cnt[2]))/3 + (cnt[2]-min(cnt[1], cnt[2]))/3
		fmt.Fprintln(out, ans)
	}
}
```