import sys
input = sys.stdin.readline

M = 3*10**5
prime = [True] * (M+1)
totient = list(range(M+1))
for i in range(2, M+1):
    if prime[i]:
        for j in range(i, M+1, i):
            if j != i:
                prime[j] = False
            totient[j] = totient[j]//i*(i-1)


def solve(N, K):
    total = 0
    for n in range(1, N+1):
        total += totient[n]
    if K >= 2*total:
        print(-1)
        return
    flip = False
    if K > total:
        K = 2*total-K
        flip = True
    D = 10**12
    lb, ub = 0, D+1
    while ub-lb > 1:
        m = (lb+ub)//2
        cnt = 0
        g = [0]*(N+1)
        for i in range(1, N+1):
            g[i] = i*m//D
        for p in range(2, N+1):
            if not prime[p]:
                continue
            for k in range(1, N//p+1)[::-1]:
                g[k*p] -= g[k]
        if sum(g) < K:
            lb = m
        else:
            ub = m
    for d in range(1, N+1):
        if (d*lb+D-1)//D <= d*ub//D:
            n = d*ub//D
            if flip:
                d, n = n, d
            print(f"{n}/{d}")
            return


T = int(input())
for _ in range(T):
    N, K = map(int, input().split())
    solve(N, K)