print("I will guess your age in 2021")
X = int(input("​Choose a number between 1 and 9"))
if 0<X<10 :
     X = 2*X
     input("Multiply your number by 2")
     X = X+5
     input ("Add 5 to your result")
     X = X*50
     input ("Multiply the result by 50")
     answer = input("Did you celebrate your birthday this year ? ")
     if answer in ["yes" , "Yes" , "Yep" , "Yeah" , "YES" , "yep" , "yeah"  "ya" ]:
      X = X + 1771
      input("Add 1771 to the result")
     elif answer in ["no" , "No" , "nn" , "Nn" , "NO" , "NO!"] :
      X = X + 1770
      input("Add 1770 to the result")
     print("You're supposed to have a four-figure number. If you don't something has gone terribly wrong.")
     input("Substract the year of your birth from your final result ")
     Y = int(input("Year of birth"))
     X = X-Y
     print(X)
     print("The first number is the one you choosed ; the last shows your age.")
     input("END")
     print("by Shadow")
else:
  print("Error")