Postfix notation is a mathematical notation in which operators follow their operands. In other words, pfexp1 pfexp2 op, where pfexp1 and pfexp2 are both postfix expressions.

Some examples:

• 2 2 + is the postfix notation of the expression 2 + 2.
• 2 3 * 1 - 5 / is the postfix notation of the expression ((2 * 3) - 1) / 5.

Here you have to compute the result from a postfix expression.

Examples

postfix("2 2 +") ➞ 4
# 2 + 2 = 4

postfix("2 3 * 1 - 5 /") ➞ 1
# ((2 * 3) - 1) / 5 = (6 - 1) / 5 = 5 / 5 = 1

Note

• Operators and operands are separated by a space.
• The operators +, -, *, / may be supported.