Time to Study

Based on the information of the time when study started and the time when study ended, check whether the total time studied in one day is t or more, and if not, create a program to find the shortage time. Time is one unit per hour, and minutes and seconds are not considered. The time is expressed in 24-hour notation in 1-hour units.

Enter the target time of study per day and the information of the time actually studied (number of studies n, start time s and end time f of each study), and check whether the total study time has reached the target. If it has reached, write "OK", and if it has not reached, write a program that outputs the insufficient time. However, the study time spent on each will not overlap.

Example: Target time	Study time	Judgment
10 hours	6:00 to 11:00 = 5 hours
12:00 to 15:00 = 3 hours
18:00 to 22:00 = 4 hours	OK
14 hours	6:00 to 11:00 = 5 hours
13:00 to 20:00 = 7 hours
2 hours shortage

Input example

Ten 3 6 11 12 15 18 22 14 2 6 11 13 20 0

Output example

OK 2

input

Given a sequence of multiple datasets. The end of the input is indicated by a single line of zeros. Each dataset is given in the following format:

t n s1 f1 s2 f2 :: sn fn

The first line gives the target time of the day t (0 ≤ t ≤ 22), and the second line gives the number of studies n (1 ≤ n ≤ 10). The following n lines are given the start time si and end time f (6 ≤ si, fi ≤ 22) of the i-th study.

The number of datasets does not exceed 100.

output

Outputs OK or missing time on one line for each dataset.

Example

Input

10 3 6 11 12 15 18 22 14 2 6 11 13 20 0

Output

OK 2

inputFormat

outputFormat

outputs the insufficient time. However, the study time spent on each will not overlap.

Example: Target time	Study time	Judgment
10 hours	6:00 to 11:00 = 5 hours
12:00 to 15:00 = 3 hours
18:00 to 22:00 = 4 hours	OK
14 hours	6:00 to 11:00 = 5 hours
13:00 to 20:00 = 7 hours
2 hours shortage

Input example

Ten 3 6 11 12 15 18 22 14 2 6 11 13 20 0

Output example

OK 2

input

Given a sequence of multiple datasets. The end of the input is indicated by a single line of zeros. Each dataset is given in the following format:

t n s1 f1 s2 f2 :: sn fn

The first line gives the target time of the day t (0 ≤ t ≤ 22), and the second line gives the number of studies n (1 ≤ n ≤ 10). The following n lines are given the start time si and end time f (6 ≤ si, fi ≤ 22) of the i-th study.

The number of datasets does not exceed 100.

output

Outputs OK or missing time on one line for each dataset.

Example

Input

10 3 6 11 12 15 18 22 14 2 6 11 13 20 0

Output

OK 2

样例

10
3
6 11
12 15
18 22
14
2
6 11
13 20
0

OK
2

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