
Mr. Malnar has finally reached his annual vacation.
The country he decided to travel to can be represented as
Mr. Malnar routinely booked the most expensive hotel in one of the cities and then started to plan his journey. To facilitate his planning, he recorded the length of the shortest path needed from the hotel to each city.
Excited about his long-awaited vacation, Mr. Malnar completely forgot in which city the hotel is located. He certainly does not want to miss the trip, so he asks you to determine in which cities the hotel can be located.
Input Specification
In the first line, there are integers
In the
In the last line, there are -1
if Mr. Malnar did not record that distance
Output Specification
In the first line, write the number of cities where the hotel can be located.
In the second line, write the labels of the cities where the hotel can be located, in ascending order.
Scoring
Subtask | Points | Constraints |
---|---|---|
1 | 10 | |
2 | 20 | |
3 | 35 | |
4 | 45 | No additional constraints. |
Sample Input 1
7 6
1 2
1 3
3 4
3 5
3 6
5 7
2 -1 -1 -1 -1 -1 3
Sample Output 1
2
4 6
Explanation for Sample 1
The path from the city labeled 4 to the city labeled 1 is of length
The same holds true for the city labeled 6.
Sample Input 2
6 6
1 2
2 3
3 4
4 5
5 6
6 1
2 -1 -1 1 -1 -1
Sample Output 2
2
3 5
Sample Input 3
4 3
1 2
2 3
3 4
1 -1 -1 1
Sample Output 3
0
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