day_18_part2.nim

import nre, strutils

proc eval(ex: string): int =
  if ex.contains('('):
    eval(ex.replace(re"\([^()]+\)", proc (match: string): string =
     $eval(match[1 .. ^2])))
  elif ex.contains('+'):
    eval(ex.replace(re"(\d+) \+ (\d+)", proc (rm: RegexMatch): string =
      $(parseInt(rm.captures[0]) + parseInt(rm.captures[1]))))
  elif ex.contains('*'):
    eval(ex.replace(re"(\d+) \* (\d+)", proc (rm: RegexMatch): string =
      $(parseInt(rm.captures[0]) * parseInt(rm.captures[1]))))
  else:
    parseInt(ex)

var sum = 0
for line in stdin.lines:
  sum += eval(line)

echo sum