Infix and postfix are the notations to write the expressions. The infix notation put operators in between the operands. The postfix notation put operators after their operands. Write a program convert from infix notation to postfix notation.

A stack is a basic data structure that insert and remove the items using last in first out (LIFO) strategy. The stack is a very powerful data structure. The stack can used when add or remove the element using last in first out order.