import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
from math import gcd
# ax = 1 (mod m)
# 
def solve(x, m):
    X = str(x)
    n = len(str(x))

    for i in range(n):
        if X[i:] == X[:n - i]:
            Y = X + X[n-i:]
            y = int(Y)
            if y % m == 0:
                return y
    
    for k in range(19 - n * 2):
        # if k + n * 2 <= 18:
        # X + Y + X が m の倍数
        # Z + 10 ** n * y % m == 0
        Z = x + x * 10 ** (n + k)
        N = 10 ** n
        M = m
        g = gcd(N, M)
        if Z % g:
            continue
        Z //= g
        N //= g
        M //= g
        y = pow(N, -1, M) * (-Z) % M
        if y < 10 ** k:
            assert (x + 10 ** n * y + 10 ** (n + k) * x) % m == 0
            return x + 10 ** n * y + 10 ** (n + k) * x


    return -1


for _ in range(ni()):
    x, m = na()
    print(solve(x, m))