#描述#
Farmer John and Bessie are playing games again. This one has to do
with troughs of water.
<BR>
<BR>
Farmer John has hidden N (1 <= N <= 10) troughs behind the barn,
and has filled some of them with food. Bessie has asked M (1 <= M
<= 100) questions of the form, "How many troughs from this list
(which she recites) are filled?".
<BR>
<BR>
Bessie needs your help to deduce which troughs are actually filled.
<BR>
<BR>
Consider an example with four troughs where Bessie has asked these
questions (and received the indicated answers):
<BR>
<BR>
1) "How many of these troughs are filled: trough 1"
--> 1 trough is filled
<BR>
2) "How many of these troughs are filled: troughs 2 and 3"
--> 1 trough is filled
<BR>
3) "How many of these troughs are filled: troughs 1 and 4"
--> 1 trough is filled
<BR>
4) "How many of these troughs are filled: troughs 3 and 4"
--> 1 trough is filled
<BR>
<BR>
From question 1, we know trough 1 is filled.
<BR>
From question 3, we then know trough 4 is empty.
<BR>
From question 4, we then know that trough 3 is filled.
<BR>
From question 2, we then know that trough 2 is empty.

#格式#
##输入格式##
（多组数据)
* Line 1: Two space-separated integers: N and M

• Lines 2..M+1: A subset of troughs, specified as a sequence of contiguous N 0's and 1's, followed by a single integer that is the number of troughs in the specified subset that are filled.

##输出格式##
* Line 1: A single line with:

• The string "IMPOSSIBLE" if there is no possible set of filled troughs
  compatible with Farmer John's answers.

• The string "NOT UNIQUE" if Bessie cannot determine from the given data
  exactly what troughs are filled.

• Otherwise, a sequence of contiguous N 0's and 1's specifying
  which troughs are filled.

#样例1#
##样例输入1##

4 4
1000 1
0110 1
1001 1
0011 1

##样例输出1##

1010

#限制#
1000ms
32768KB

#提示#

#来源#