package main

import . "fmt"
import . "strings"

func main() {
	var t int
	Scan(&t)
	for ; t > 0; t-- {
		var k int
		var s string
		Scan(&k, &s)
		ans := (Repeat(s[0:1], min(k, len(s))) + s)[:len(s)]
		Println(ans)
	}
}