from sys import stdin
input=lambda :stdin.readline()[:-1]

M=3*10**5+5
sieve=[0]*2+[1]*M
primes=[]
for p in range(2,M):
  if sieve[p]:
    for i in range(2*p,M,p):
      sieve[i]=0

def calc(n,p):
  dp=[0]*(n+1)
  for i in range(1,n+1):
    dp[i]=(p*i)>>38
  for p in range(n,1,-1):
    if sieve[p]:
      for i in range(n//p,0,-1):
        dp[i*p]-=dp[i]
  return sum(dp)

m=1<<38
def solve():
  n,k=map(int,input().split())
  c=calc(n,m-1)
  if k==c+1:
    print('1/1')
    return
  if k<=c:
    rev=False
  elif k<=2*c+1:
    rev=True
    k=2*c+2-k
  else:
    print(-1)
    return
  ng,ok=0,1<<38
  for _ in range(38):
    mid=(ok+ng)>>1
    if calc(n,mid)>=k:
      ok=mid
    else:
      ng=mid
  
  ans=-1
  for p in range(1,n+1):
    q=(ok*p)>>38
    if m*q>ng*p:
      if rev:
        p,q=q,p
      print(str(q)+'/'+str(p))
      return
    
  raise Exception

for _ in range(int(input())):
  solve()