user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: the picul is used as a measurement of mass in what system? 
Knowledge Triplets: Chinese units of measurement, measurement_unit.measurement_system.weight_units, Picul
Mass, measurement_unit.dimension.units, Electron rest mass
Mass, measurement_unit.dimension.units, Cental
Mass, measurement_unit.dimension.units, Troy pound
Chinese units of measurement, measurement_unit.measurement_system.length_units, Cun
Mass, measurement_unit.dimension.units, MeV/c²
m.0t081jw, type.object.permission, m.019h
Chinese units of measurement, measurement_unit.measurement_system.length_units, Li
Picul, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
Mass, measurement_unit.dimension.units, Tael
Mass, measurement_unit.dimension.units, Kilogram
Mass, measurement_unit.dimension.units, Planetary mass
Mass, measurement_unit.dimension.units, Planck mass
picul.noun.01, base.wordnet.synset.syntactic_category, Noun
Mass, measurement_unit.dimension.si_base_unit, Kilogram
Mass, measurement_unit.dimension.units, Short ton
Mass, measurement_unit.dimension.units, Picul
Mass, measurement_unit.dimension.units, Short quarter
m.0t081jw, dataworld.gardening_hint.last_referenced_by, Picul
Wired, base.yupgrade.user.topics, Mass
Mass, measurement_unit.dimension.units, Pound
Mass, measurement_unit.dimension.units, Earth mass
Mass, measurement_unit.dimension.units, Dram
weight unit.noun.02, base.wordnet.synset.hyponymy, picul.noun.01
noun.quantity, base.wordnet.lexical_name.synsets, picul.noun.01
Mass, measurement_unit.dimension.units, Solar mass
Cun, measurement_unit.distance_unit.measurement_system, Chinese units of measurement
Candareen, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
Mass, measurement_unit.dimension.units, Atomic mass unit
m.07s3ffv, base.wordnet.word_sense.sense, picul.noun.01
m.07nfbgl, base.ontologies.ontology_instance_mapping.freebase_topic, Mass
Mass, measurement_unit.dimension.units, Stone
Mass, measurement_unit.dimension.units, Mace
Mass, measurement_unit.dimension.units, Hundredweight
m.019h, type.permission.controls, m.0t081jw
Mass, user.avh.default_domain.ellerdale_topic.ellerdale_id, 0080-0198
Picul, measurement_unit.mass_unit.weightmass_in_kilograms, 60.478982
m.075_7gq, base.yupgrade.user.topics, Mass
picul.noun.01, base.wordnet.synset.hypernym, weight unit.noun.02
picul.noun.01, base.wordnet.synset.lexname, noun.quantity
Mass, measurement_unit.dimension.units, Cash
Chinese units of measurement, user.movgp0.default_domain.measurement_system.unit_of_lenght, Li
Mass, base.ontologies.ontology_instance.equivalent_instances, m.07nfbgl
Ana Marie Cox, base.yupgrade.user.topics, Mass
Chinese units of measurement, measurement_unit.measurement_system.weight_units, Candareen
Mass, measurement_unit.dimension.units, Pennyweight
Mass, base.schemastaging.context_name.pronunciation, g.125_l6gm1
m.0tj44mw, dataworld.gardening_hint.last_referenced_by, m.0t081jw
m.0qplrls, dataworld.gardening_hint.last_referenced_by, Mass
Chinese units of measurement, measurement_unit.measurement_system.weight_units, Tael
Mass, measurement_unit.dimension.units, Troy ounce
Mass, base.skosbase.vocabulary_equivalent_topic.equivalent_concept, Mass (Physics)
picul.noun.01, base.wordnet.synset.word, m.07s3ffv
Mass, measurement_unit.dimension.units, Tonne
Mass, measurement_unit.dimension.units, Milligram
Tael, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
Mass, measurement_unit.dimension.units, Long ton
g.125_q7_ls, base.schemastaging.pronunciation.yomigana, たん
Mass, measurement_unit.dimension.units, Candareen
Mass, measurement_unit.dimension.units, Long quarter
Chinese units of measurement, measurement_unit.measurement_system.weight_units, Catty
Mass, measurement_unit.dimension.units, Jupiter mass
Mass, measurement_unit.dimension.units, Microgram
Mass, measurement_unit.dimension.units, Carat
Picul, measurement_unit.measurement_system.weight_units, Chinese units of measurement
Mass, measurement_unit.dimension.units, Grain
Chinese units of measurement, measurement_unit.measurement_system.weight_units, Cash
Mass, measurement_unit.dimension.units, Catty
Picul, base.schemastaging.context_name.pronunciation, g.125_q7_ls
Li, measurement_unit.distance_unit.measurement_system, Chinese units of measurement
m.07vn7ph, base.yupgrade.user.topics, Mass
Mace, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
Mass, measurement_unit.dimension.units, Ounce
Mass (Physics), base.skosbase.skos_concept.equivalent_topic, Mass
Catty, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
Chinese units of measurement, measurement_unit.measurement_system.weight_units, Mace
Mass, measurement_unit.dimension.units, Gram
picul.noun.01, base.wordnet.synset.equivalent_topic, Picul
Cash, measurement_unit.mass_unit.measurement_system, Chinese units of measurement
mass.noun.01, base.wordnet.synset.equivalent_topic, Mass

Answer: Chinese units of measurement