ans = []

def count_leading_zero(s: str) -> int:
    res = 0
    for c in s:
        if (c == '0'): res += 1
        else: break
    return res

def modify(s: str, l: int, r: int, base: int = 0) -> str:
    # assert(base == 0)
    if (l >= r): return s
    src = s[l:r + 1]
    src = int(src, base=3)
    src = bin(src)[2:]
    ans.append((l + 1 + base, r + 1 + base, f"before: {s}, after: {s[:l] + src + s[r + 1:]}"))
    return s[:l] + src + s[r + 1:]

def erase_trailing_zero(s: str, base: int) -> str:
    l, r = len(s) - 1, len(s) - 1
    while (l >= 0 and s[l] == '0'): l -= 1
    l += 1
    assert(l >= 1)
    return modify(s, l, r, base)

def change_last_digit(s: str, base: int):
    l = len(s) - 2
    while (s[l] == '0'): l -= 1
    assert(l >= 1)
    assert(len(s) >= 4)
    s = modify(s, l, len(s) - 1, base)
    return s
    # if (s[-1] == '1'):
    #     s = s[:-1]
    #     s = erase_trailing_zero(s, base)
    #     s = s + '1'
    #     if (s[:-2] == '0'):
    #         return modify(s, len(s) - 3, len(s) - 1, base)
    #     else:
    #         return modify(s, len(s) - 2, len(s) - 1, base)
    # else:
    #     s = erase_trailing_zero(s, base)
    #     return modify(s, len(s) - 2, len(s) - 1, base)

def cleanup(s: str, base: int):

    for i in range(1, len(s)):
        if (s[i] == '0'):
            s = modify(s, i - 1, i, base)
    for i in range(len(s) - 1, 0, -1):
        s = modify(s, i - 1, i, base)
    s = erase_trailing_zero(s, base)
    return s

def solve() -> None:
    ans.clear()
    s = input()
    t = input()

    # 1) remove all leading 0's
    # s_lz = count_leading_zero(s)
    # t_lz = count_leading_zero(t)
    # if (s_lz < t_lz):
    #     print(-1)
    #     return
    # s = modify(s, 0, s_lz - t_lz)
    # base = count_leading_zero(s)
    # s, t = s[base:], t[base:]
    base = 0
    # print("1st: ", s, t)


    # 2) check if s == 1 or t == 1
    if (len(s) == 1 or len(t) == 1):
        if (s != t):
            print(-1)
        else:
            print(len(ans))
            for (l, r, _) in ans:
                print(l, r)
        return
    # print("2nd: ", s, t)

    assert (len(s) >= 2)
    # 至多操作两次长度即为3
    if (len(s) == 2): s = modify(s, 0, 1, base)
    if (len(s) == 2): s = modify(s, 0, 1, base)
    assert (len(s) >= 3)

    # 3) expand s to length(t)
    while (len(t) > 2):
        assert(len(s) >= 3)
        # 保证第2位是1且长度至少为4
        if (len(s) == 3): s = modify(s, 0, 2, base)
        if (s[1] == '0'): s = modify(s, 0, 1, base)
        
        if (s[-1] != t[-1]):
            s = change_last_digit(s, base)
        s, t = s[:-1], t[:-1]

        s = erase_trailing_zero(s, base)

        # print("3rd in progress: ", s, t)    
    
    # print("3rd: ", s, t)

    # 4) cleanup
    s = cleanup(s, base)

    # print("4th: ", s, t)

    # 5) check if s != t
    if (t == '11'):
        s = modify(s, 0, 1, base)

    assert(s == t)

    if (len(ans) > 512):
        while True:
            pass

    print(len(ans))
    for (l, r, debug) in ans:
        print(l, r)
        # print(debug)
    

def main():
    t = int(input())
    for _ in range(t): solve()

if (__name__ == "__main__"):
    main()