('CID100244924', 1),Oxamicacid, (p-chlorobenzyl)-, ethyl ester (7CI,8CI)
('CID103080614', 1),Oxamicacid, (carboxymethyl)- (7CI,8CI)
ldiff: defaultdict(<type 'list'>, {'CID100244924': [42], 'CID103080614': [28]})
f1: [42]
f2: [28]
c1: Counter({42: 1})
c2: Counter({28: 1})
The chosen was  ... CID103080614