output_description: Output the converted Celsius temperature in a line.
input_description: The input is given in the following format.
  
      
      
      $F$
      
  
  The input line provides a temperature in Fahrenheit $F$ ($30 \leq F \leq
  100$), which is an integer divisible by $2$.
attempt: kashi = int(input())
  sesshi = int((kashi - 30) / 2)
  print(sesshi)
  
problem_description: Celsius/Fahrenheit
  
  In Japan, temperature is usually expressed using the Celsius (℃) scale. In
  America, they used the Fahrenheit (℉) scale instead. $20$ degrees Celsius is
  roughly equal to $68$ degrees Fahrenheit. A phrase such as "Today’s
  temperature is $68$ degrees" is commonly encountered while you are in America.
  
  A value in Fahrenheit can be converted to Celsius by first subtracting $32$
  and then multiplying by $\frac{5}{9}$. A simplified method may be used to
  produce a rough estimate: first subtract $30$ and then divide by $2$. Using
  the latter method, $68$ Fahrenheit is converted to $19$ Centigrade, i.e.,
  $\frac{(68-30)}{2}$.
  
  Make a program to convert Fahrenheit to Celsius using the simplified method:
  $C = \frac{F - 30}{2}$.
samples: [{"input": "68", "output": "19"}, {"input": "50", "output": "10"}]