output_description: If N_1, N_2, N_3 and N_4 can be arranged into the sequence of digits "1974",
  print `YES`; if they cannot, print `NO`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N_1 N_2 N_3 N_4
attempt: n=sorted(list(map(int,input().split())))
  if n=[1,4,7,9]:
    print("YES")
  else:
    print("NO")
problem_description: Statement
  
  You are given four digits N_1, N_2, N_3 and N_4. Determine if these can be
  arranged into the sequence of digits "1974".
samples: [{"input": "1 7 9 4", "output": "YES\n    \n\nWe can get 1974 by swapping N_2 and N_3.\n\n* * *"}, {"input": "1 9 7 4", "output": "YES\n    \n\nWe already have 1974 before doing anything.\n\n* * *"}, {"input": "1 2 9 1", "output": "NO\n    \n\n* * *"}, {"input": "4 9 0 8", "output": "NO"}]