Arithmetica v1.3

Time limit = 5 seconds

Input. The first line of input contains integer N (N < 100). Then N lines follow. Each line is a command. Command is either definition of a function or an identifier.

alpha	   ::= a-zA-Z
numeric	   ::= 0-9
command    ::= identifier | definition
definition ::= identifier ':=' expression
identifier ::= alpha +
expression ::= '(' expression ')' | integer_number | identifier | expression ('+' | '*' | '-') expression
integer_number ::= '-' ? numeric+

If command is definition, then nothing should be output.

If command is identifier,then it should be interpreted as requests to calculate function: "calculate the value of the function and output result".

Each function should have no more than one definition. In input definitions go first, requests to calculate functions follow them. The length of each input line is less than 1000.

Output. For each request to calculate a function your program should output one line with the result of calculation. If the recursion depth of the requested function is infinity or some envolved functions (identifies) are not defined, then the result should be 'error'. Otherwise the result is numerical value of the function.

It is known that all numbers and values of functions are less than 2³⁰ in absolute value.

2
a:=1+2*3
a

9

2
a:=b-b
a

error

3
b:=a*2
a:=(1+3)*3
b

24

8
b:=a*2
a:=(1+3)*3
c:=a+b+d
d:=a+c
e:=(b-a)
b
c
e

24
error
12

Author:
Voroztsov Artem
18 May 2003

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