output_description: Print the abbreviation for the N-th round of ABC.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: n, m = map(int, input().split())
  a = [[int(i) for i in input().split()] for j in range(m)]
  a.sort(key=lambda x: x[1])
  a.sort(key=lambda x: x[0])
  cc = 0
  for i in range(m):
      if a[i][0] == 1:
          for j in range(i, m):
              if a[i][1] == a[j][0] and a[j][1] == n:
                  cc = 1
                  break
      if cc == 1:
          break
  print("POSSIBLE" if cc == 1 else "IMPOSSIBLE")
  
problem_description: Statement
  
  This contest, _AtCoder Beginner Contest_ , is abbreviated as _ABC_.
  
  When we refer to a specific round of ABC, a three-digit number is appended
  after ABC. For example, ABC680 is the 680th round of ABC.
  
  What is the abbreviation for the N-th round of ABC? Write a program to output
  the answer.
samples: [{"input": "100", "output": "ABC100\n    \n\nThe 100th round of ABC is ABC100.\n\n* * *"}, {"input": "425", "output": "ABC425\n    \n\n* * *"}, {"input": "999", "output": "ABC999"}]