Example exam by Ellen
Ellen is teaching elementary math to her students and the
time for the final exam has come. The exam consists of
$n$ questions. In each
question the students have to add (
$+$), subtract (
$$) or multiply (
$*$) a pair of numbers.
Ellen has already chosen the $n$ pairs of numbers. All that remains
is to decide for each pair which of the three possible
operations the students should perform. To avoid students
getting bored, Ellen wants to make sure that the $n$ correct answers to her exam are
all different.
Please help Ellen finish constructing the exam by automating
this task.
Input
The input consists of:

one line with one integer $n$ ($1\leq n \leq 2\, 500$), the
number of pairs of numbers;

$n$ lines each with
two integers $a$ and
$b$ ($10^6 \leq a, b \leq 10^6$), a
pair of numbers used.
Output
For each pair of numbers $(a,b)$ in the same order as in the
input, output a line containing a valid equation. Each equation
should consist of five parts: $a$, one of the three operators,
$b$, an equals sign
($=$), and the result of
the expression. All the $n$ expression results must be
different.
If there are multiple valid answers you may output any of
them. If there is no valid answer, output a single line with
the string “impossible” instead.
Sample Input 1 
Sample Output 1 
4
1 5
3 3
4 5
1 6

1 + 5 = 6
3 * 3 = 9
4  5 = 1
1  6 = 5

Sample Input 2 
Sample Output 2 
4
4 2
4 2
4 2
4 2

impossible
