output_description: Print the computational result in a line.
input_description: An expression is given in a line. Two consequtive symbols (operand or
  operator) are separated by a space character.
  
  You can assume that +, - and * are given as the operator and an operand is a
  positive integer less than 106
problem_description: Input
  
  An expression is given in a line. Two consequtive symbols (operand or
  operator) are separated by a space character.
  
  You can assume that +, - and * are given as the operator and an operand is a
  positive integer less than 106
samples: [{"input": "1 2 +", "output": "3"}, {"input": "1 2 + 3 4 - *", "output": "-3"}]