('CID106424355', 2),L-leucine, N-ethoxycarbonyl-, Nonyl Ester
('CID106424355', 2),l-Leucine, N-ethoxycarbonyl-, nonyl ester
('CID106424387', 2),l-Leucine, N-ethoxycarbonyl-, tridecyl ester
('CID106424387', 2),L-leucine, N-ethoxycarbonyl-, Tridecyl Ester
ldiff: defaultdict(<type 'list'>, {'CID106424355': [13, 13], 'CID106424387': [16, 16]})
f1: [13, 13]
f2: [16, 16]
c1: Counter({13: 2})
c2: Counter({16: 2})
The chosen was ... CID106424355