('CID100116681', 2),L-Asparticacid, N-(1-oxo-2-propenyl)- (9CI)
('CID100116681', 2),L-Asparticacid, N-(1-oxo-2-propenyl)-, disodium salt (9CI)
('CID100196643', 1),L-Asparticacid, N-(N2-L-seryl-L-lysyl)-
ldiff: defaultdict(<type 'list'>, {'CID100196643': [25], 'CID100116681': [29, 44]})
f1: [29, 44]
f2: [25]
c1: Counter({44: 1, 29: 1})
c2: Counter({25: 1})
The chosen was  ... CID100196643