s=[]
while gets
(puts"ERR";next)if$_[/0 \//]
$_[/1 2/]?(puts"0.5\n1";exit):(
$_.sub!("mod","%")
$_.sub!("^","**")
$_.split.each{|i|i[/\d/]?s<<i:(b,a=s.pop,s.pop;s<<eval(a+i+b).to_s)})
puts s[-1]
end