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def get_mrna(mrna):
start_code = 'AUG'
end_code = ['UAA','UAG','UGA']
st_num = mrna.find(start_code)
e1_num = mrna.find(end_code[0])
e2_num = mrna.find(end_code[1])
e3_num = mrna.find(end_code[2]
if (e1_num - st_num) % 3 == 1:
print(mrna[st_num+3:e1_num]
if (e2_num - st_num) % 3 == 1:
print(mrna[st_num+3:e1_num])
if (e3_num - st_num) % 3 == 1:
print(mrna[st_num+3:e1_num])