[{"from": "human", "value": "Given SMILES, write its poly dispersity index at room temperature and atmospheric pressure. ->  CC1=CC(CCCCCCCCCCCC)=C(C2=CC=C(C3=CC=C(C4=C(CCCCCCCCCCCC)C=C(C5=CC(CCCCCCCCCCCC)=C(C6=CC=C(C7=CC=C(C8=C(CCCCCCCCCCCC)C=C(C)[Se]8)[Se]7)[Se]6)[Se]5)S4)S3)S2)S1\n"}, {"from": "gpt", "value": " 1.99\n"}]