import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import gcd,log

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

from collections import deque
class Dinic:
    def __init__(self, N):
        self.N = N
        self.G = [[] for i in range(N)]

    def add_edge(self, fr, to, cap):
        forward = [to, cap, None]
        forward[2] = backward = [fr, 0, forward]
        self.G[fr].append(forward)
        self.G[to].append(backward)

    def add_multi_edge(self, v1, v2, cap1, cap2):
        edge1 = [v2, cap1, None]
        edge1[2] = edge2 = [v1, cap2, edge1]
        self.G[v1].append(edge1)
        self.G[v2].append(edge2)

    def bfs(self, s, t):
        self.level = level = [None]*self.N
        deq = deque([s])
        level[s] = 0
        G = self.G
        while deq:
            v = deq.popleft()
            lv = level[v] + 1
            for w, cap, _ in G[v]:
                if cap and level[w] is None:
                    level[w] = lv
                    deq.append(w)
        return level[t] is not None

    def dfs(self, v, t, f):
        if v == t:
            return f
        level = self.level
        for e in self.it[v]:
            w, cap, rev = e
            if cap and level[v] < level[w]:
                d = self.dfs(w, t, min(f, cap))
                if d:
                    e[1] -= d
                    rev[1] += d
                    return d
        return 0

    def flow(self, s, t):
        flow = 0
        INF = 10**9 + 7
        G = self.G
        while self.bfs(s, t):
            *self.it, = map(iter, self.G)
            f = INF
            while f:
                f = self.dfs(s, t, INF)
                flow += f
        return flow

def floor_sum(n: int, m: int, a: int, b: int) -> int:
    ans = 0

    if a >= m:
        ans += (n - 1) * n * (a // m) // 2
        a %= m

    if b >= m:
        ans += n * (b // m)
        b %= m

    y_max = (a * n + b) // m
    x_max = y_max * m - b

    if y_max == 0:
        return ans

    ans += (n - (x_max + a - 1) // a) * y_max
    ans += floor_sum(y_max, a, m, (a - x_max % a) % a)

    return ans

M = 3*10**5 + 1
mebius = [1] * (M+1)
prime = [True] * (M+1)
for p in range(2,M+1):
    if not prime[p]:
        continue
    for n in range(p,M+1,p):
        if n%(p*p) == 0:
            mebius[n] = 0
        mebius[n] *= -1
        prime[n] = False

mebius_cum = [mebius[n] for n in range(M+1)]
mebius[0] = 0
for n in range(1,M):
    mebius_cum[n+1] += mebius_cum[n]

def solve(N,K):
    lower = (0,1)
    upper = (1,0)

    calc = 0

    def cond(p,q):
        nonlocal calc
        calc += 1
        #assert p <= N  and q <= N
        """
        ・qx<=py
        ・1 <= x,y <= N
        ・gcd(x,y)=1
        をみたすx,yを数える

        gcd(x,y)がkの倍数とすると

        sum((N//k)-(qi)//p for i in range(1,(N//k)+1))
        -> floor_sum

        +メビウス変換
        """

        res = 0
        B = int(N**.5)
        for k in range(1,B+1):
            t = N//k
            tmp = 0

            ok = 0
            ng = t
            while ng-ok>1:
                mid = (ok+ng)//2
                if (q*mid+q)//p <= t:
                    ok = mid
                else:
                    ng = mid
            
            tmp = (t+1) * ng - floor_sum(ng,p,q,q)
            res += tmp * mebius[k]
        
        
        for t in range(1,N//(B+1)+1):
            
            k_l = N//(t+1)+1
            k_r = N//t

            tmp = 0
            ok = 0
            ng = t
            while ng-ok>1:
                mid = (ok+ng)//2
                if (q*mid+q)//p <= t:
                    ok = mid
                else:
                    ng = mid
            
            tmp = (t+1) * ng - floor_sum(ng,p,q,q)
            res += tmp * (mebius_cum[k_r] - mebius_cum[k_l-1])

        
        return res

    if cond(N,1) < K:
        print(-1)
        return 

    while True:
        a,b = lower
        c,d = upper
        p,q = (a+c,b+d)

        if a+b >= N and c+d >= N:
            print(-1)
            return 

        check = cond(p,q)
        if  check < K:
            """
            右に潜る
            """
            ok = 1
            if d!=0:
                ng = min((N-b)//d,(N-a)//c) + 1
            else:
                ng = (N-a)//c + 1
            while ng-ok>1:
                mid = (ok+ng)//2
                p,q = a+c*mid,b+d*mid
                xxx = cond(p,q)
                if  xxx < K:
                    ok = mid
                elif K < xxx:
                    ng = mid
                else:
                    p,q = a+c*mid,b+d*mid
                    print("{}/{}".format(p,q))
                    return 
            lower = (a+c*ok,b+d*ok)
        elif K < check:
            """
            左に潜る
            """
            ok = 1
            if a!=0:
                ng = min((N-d)//b,(N-c)//a) + 1
            else:
                ng = (N-d)//b + 1
            
            while ng-ok>1:
                mid = (ok+ng)//2
                p,q = a*mid+c,b*mid+d
                if cond(p,q) > K:
                    ok = mid
                else:
                    ng = mid
            upper = (a*ok+c,b*ok+d)
        else:
            print("{}/{}".format(p,q))
            return 

for _ in range(int(input())):
    N,K = mi()
    solve(N,K)