Expressions: The set of strings that look like arithmetic expressions using nonnegative integers and the operations , -, *, /, and parentheses to group terms. For example, the following are properly formatted arithmetic expressions: 0, 2, 2 30, 2 30*401, (2 30)*401/(23 0), (((1 2)/3-4)*5 6)*7 The following are not: 02, (2 30, 2 30*401 , (2 30)*401), -4, 2 3, (), 2*(), 1 2)*3-4)*5 6)*7