School holidays come in Berland. The holidays are going to continue for *n* days. The students of school №*N* are having the time of their lives and the IT teacher Marina Sergeyevna, who has spent all the summer busy checking the BSE (Berland State Examination) results, has finally taken a vacation break! Some people are in charge of the daily watering of flowers in shifts according to the schedule. However when Marina Sergeyevna was making the schedule, she was so tired from work and so lost in dreams of the oncoming vacation that she perhaps made several mistakes. In fact, it is possible that according to the schedule, on some days during the holidays the flowers will not be watered or will be watered multiple times. Help Marina Sergeyevna to find a mistake.
The first input line contains two numbers *n* and *m* (1 ≤ *n*, *m* ≤ 100) — the number of days in Berland holidays and the number of people in charge of the watering respectively. The next *m* lines contain the description of the duty schedule. Each line contains two integers *a*<sub class="lower-index">*i*</sub> and *b*<sub class="lower-index">*i*</sub> (1 ≤ *a*<sub class="lower-index">*i*</sub> ≤ *b*<sub class="lower-index">*i*</sub> ≤ *n*), meaning that the *i*-th person in charge should water the flowers from the *a*<sub class="lower-index">*i*</sub>-th to the *b*<sub class="lower-index">*i*</sub>-th day inclusively, once a day. The duty shifts are described sequentially, i.e. *b*<sub class="lower-index">*i*</sub> ≤ *a*<sub class="lower-index">*i* + 1</sub> for all *i* from 1 to *n* - 1 inclusively.
a = input().split()
s = {}
for i in range(int(a[0])):
    s[i+1] = 0
for i in range(int(a[1])):
    d = input().split()
    for j in range(int(d[0]),int(d[1]) + 1):
        s[j] += 1
for i in s:
    if s[i] != 1:
        print(i,s[i])
        exit()
print("OK")