Write a program in which the driver simply calls a function
named inToPostfix which reads an infix expression from
standard input and writes the equivalent postfix expression
to standard output. The infix expression includes operands,
parentheses, and operators, where the operands are single
lowercase characters, and the operators are +, -, *, /, and
Use the STL container stack to store a stack of characters.
Include error checks in the code.
Your program should be implemented in a single file.