Witnesses, numbered from 1 to n, have made their testimonies in a court. Each testimony is a statement of the form: "the i-th witness agrees with the j-th witness" or "the i-th witness does not agree with the j-th witness".

If the i-th witness agrees with the j-th witness then he agrees also with all the witnesses that the j-th witness agrees with. Similarly, the i-th witness does not agree with all the witnesses that the j-th witness does not agree with.

We say that witness A is not credible if from testimonies made in a court it follows that there exists a witness B such that A agrees with B and A does not agree with B.

Task

• reads the number of witness and their testimonies from the input file WIA.IN,
• finds all the witnesses that are not credible,
• writes the result to the text file WIA.OUT.

Input

In the second line of the text file WIA.IN there is a single integer m, 0 <= m <= 8000, which is the number of testimonies.

In each of the following m lines there are two integers i, j (1 <= i <= n, 1 <= | j | <= n), separated by a single space. If j is positive it describes a testimony: "the i-th witness agrees with the j-th witness". If j is negative it means: "the i-th witness does not agree with the (-j)-th witness".

Output

• a single word NIKT (which means NOBODY in Polish), if it follows from testimonies that there is no witness that is not credible,
• or - in increasing order - the numbers of witnesses that are not credible (one member in one line).

Example

6
12
1 3
1 6
2 -1
3 4
4 1
4 -2
4 5
5 -1
5 -3
5 2
6 5
6 4

1
3
4
6