Problem B

RPN Calculator

A RPN (Reverse Polish Notation) calculator uses post-fixes operands. For example, to add two numbers, you get one, then the other and, finally, the addition operator:

     5 2 -

The previous example is the operation $5-2$ in RPN notation.

Problem

In this problem, we want to implement a simple RPN calculator with the four basic arithmetic operators (+, -, * and /) and the assignment. The assignment returns the assigned value.

The tool should read from STDIN an expression by line, and write to STDOUT a result by line. Consider that all lines have the correct syntax.

Input

The input consists of a sequence of expressions. Each expression is contained in a single line. Variables can be defined and used in different lines.

2 2 + 3 -
1 2 3 * +
a 10 =
a 2 / 2 2 + +
-2 -3 +
a 10 = b 5 = +

Output

The output contains the results of evaluating each one of the expressions.

1
7
10
9
-5
15