#/***********************************************************
#    eval.rb -- 式の評価
#***********************************************************/

$ch = 0

def isdigit( c )
    if (c < ?0 || c > ?9); false; else; true; end
end

def error(s)  # エラー処理 
    printf("%s\n", s);  exit 1
end

def readch  # 1文字を読む. 空白は読み飛ばす. 
    begin 
        if (($ch = $stdin.getc) == nil); return false; end
    end while ($ch == ?\s || $ch == ?\t)
    true
end

def number  # 数 
    if ($ch == ?+ || $ch == ?-) 
        sign = $ch;  readch
    end
    if (! isdigit($ch)); error("数か '(' がありません"); end
    x = $ch - ?0
    while (readch && isdigit($ch))
        x = 10 * x + $ch - ?0
    end
    if ($ch == ?.) 
        a = 1
        while (readch && isdigit($ch))
            x += (a /= 10.0) * ($ch - ?0)
        end
    end
    if (sign == ?-); return -x; else; return x; end
end

def factor  # 因子 
    if ($ch != ?(); return number; end
    readch;  x = expression
    if ($ch != ?)); error("')' がありません"); end
    readch;  return x
end

def term  # 項 
    x = factor
    while (true)
        if ($ch == ?*) 
            readch;  x *= factor
        elsif ($ch == ?/) 
            readch;  y = factor
            if (y == 0); error("0 では割れません"); end
            x /= y.to_f
        else
            break
        end
    end
    return x
end

def expression  # 式 
    x = term
    while (true)
        if ($ch == ?+) 
            readch;  x += term
        elsif ($ch == ?-) 
            readch;  x -= term
        else
            break
        end
    end
    return x
end

readch;  x = expression
if ($ch != ?\n); error("文法の間違いがあります"); end
printf("%g\n", x)

exit 0