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  1. import sys
  2.  
  3. n = int(sys.stdin.readline())
  4.  
  5. def trib(n):
  6. if n == 1 or n == 2 or n == 3:
  7. return 1
  8. else:
  9. return trib(n - 1) + trib(n - 2) + trib(n - 3)
  10.  
  11. print(trib(n))
Success #stdin #stdout 3.41s 14156KB
stdin
30
stdout
20603361