('CID100006966', 1),Pyromelliticacid dianhydride
('CID100085646', 1),Pyromelliticacid, 1,4-diethyl ester (6CI)
ldiff: defaultdict(<type 'list'>, {'CID100006966': [12], 'CID100085646': [25]})
f1: [12]
f2: [25]
c1: Counter({12: 1})
c2: Counter({25: 1})
The chosen was ... CID100006966