#!/bin/python3

import sys


t = int(input().strip())
for a0 in range(t):
    n,k = input().strip().split(' ')
    n,k = [int(n),int(k)]
    num = input().strip()
    # prefix array
    marr = [int(num[0])]
    for i in range(1,len(num)):
        marr.append(marr[-1](int(num[i])))
    #print(marr)
    res = 0
    #find max prodcut
    for i in range(k,len(marr)):
        if marr[i-k] !=0:
            prod = marr[i]//marr[i-k]
        res=max(prod , res )
    res = max(res,marr[k-1])
    print(res)