```go
package main

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

func main() {
	reader := bufio.NewReader(os.Stdin)
	var t int
	fmt.Fscan(reader, &t)
	for i := 0; i < t; i++ {
		var n int
		fmt.Fscan(reader, &n)
		var ss string
		fmt.Fscan(reader, &ss)
		s := []byte(ss)
		var seen [26][26]bool
		ans := false
		for k := 1; k <= n; k++ {
			if k >= 2 && k <= n-1 {
				c1 := int(s[k-1] - 'a')
				c2 := int(s[k] - 'a')
				if seen[c1][c2] {
					ans = true
				}
			}
			if k >= 2 {
				prev := int(s[k-2] - 'a')
				curr := int(s[k-1] - 'a')
				seen[prev][curr] = true
			}
		}
		if ans {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}
```