import math
from collections import deque
from heapq import heapify,heappop,heappush
import sys
def find(u, par):
if par[u] != u:
par[u] = find(par[u], par)
return par[u]
def union(u, v, par, size):
u_root = find(u, par)
v_root = find(v, par)
if u_root == v_root:
return
if size[u_root] < size[v_root]:
par[u_root] = v_root
size[v_root] += size[u_root]
else:
par[v_root] = u_root
size[u_root] += size[v_root]
def ip():
return map(int,input().split())
res=[]
T=1
T=int(input())
for __ in range(T):
s=str(input())
t=int(input())
pq=[]
heapify(pq)
n=len(s)
if n==1:
res.append(s[0])
continue
for i in range(n-1):
if s[i]>s[i+1]:
heappush(pq,i)
l=[i-1 for i in range(n)]
r=[i+1 for i in range(n)]
d=[False for _ in range(n)]
curr=n
ct=0
fg=False
while pq:
if ct+curr>=t:
rem=t-ct
c=0
for i in range(n):
if not d[i]:
c+=1
if c==rem:
res.append(s[i])
fg=True
break
break
i=heappop(pq)
d[i]=True
# print(i)
# print(pq)
# print(l)
# print(r)
if i+1<n:
l[r[i]]=l[i]
if i-1>=0:
r[l[i]]=r[i]
if 0<=l[i]<n and 0<=r[i]<n:
if s[l[i]]>s[r[i]]:
heappush(pq,l[i])
ct+=curr
curr-=1
# print("after")
# print(pq)
# print(l)
# print(r)
j=n-1
if fg:
continue
while True:
if ct+curr>=t:
rem=t-ct
c=0
for i in range(n):
if not d[i]:
c+=1
if c==rem:
res.append(s[i])
fg=True
break
break
while j>=0 and d[i]:
j-=1
d[j]=True
ct+=curr
curr-=1
print("".join(res))
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