rank nation gold silver bronze total
rank
nation
gold
silver
bronze
total
number
number
number
number
number
number text number number number number
1 brazil 21 9 12 42
what is the difference between the amount of bronze medals won by the us and the amount of silver medals ?
WP VBD-AUX DT NN IN DT NN IN NN NNS VBN IN DT NNP CC DT NN IN NN NNS .