from math import gcd

def inverse(n, d, MOD):
    return n * pow(d, -1, MOD) % MOD

for _ in range(int(input())):
    X, M = map(int, input().split())

    if X%M == 0:
        print(X)
        continue

    sX = str(X)
    L = len(sX)
    flag = False
    for i in range(1, L):
        if sX[i:] == sX[:-i] and int(sX+sX[L-i:])%M == 0:
            print(sX+sX[L-i:])
            flag = True
            break
    if flag:
        continue

    if (X*10**L+X)%M == 0:
        print(X*10**L+X)
        continue

    GCD = gcd(M, 10**L)
    for n in range(1, 18-L*2+1):
        m = (X+X*10**(L+n))%M
        if m == 0:
            print(sX+"0"*n+sX)
            break
        if m%GCD != 0:
            continue
        if 10**L < M:
            a = 10**L
            g = M-m
            G = gcd(a, M)
            a //= G
            g //= G
            mo = M//G
            x = inverse(g, a, mo)
            if x < 10**n:
                sx = str(x)
                while len(sx) < n:
                    sx = "0"+sx
                print(sX+sx+sX)
                break
        else:
            a = 10**L%M
            g = M-m
            G = gcd(a, M)
            a //= G
            g //= G
            mo = M//G
            x = inverse(g, a, mo)
            if x < 10**n:
                sx = str(x)
                while len(sx) < n:
                    sx = "0"+sx
                print(sX+sx+sX)
                break
    else:
        print(-1)