I think we are missing something which is quite common in this case.

http://ideone.com/XHozKe

Can someone throw some ideas, why this fails at test case 7?

___Test
13
Fominykh Isenbaev BBB
BBB CCC AAA
Ayzenshteyn Oparin Samsonov
Ayzenshteyn Chevdar Samsonov
Dublennykh Fominykh Ivankov
Burmistrov Dublennykh Kurpilyanskiy
Cormen Leiserson Rivest
Oparin AA AAA
Isenbaev Oparin Toropov
AA DD PP
PP QQ RR
RR SS TT
TT Toropov Oparin

____correct answer:
AA 2
AAA 2
Ayzenshteyn 2
BBB 1
Burmistrov 3
CCC 2
Chevdar 3
Cormen undefined
DD 3
Dublennykh 2
Fominykh 1
Isenbaev 0
Ivankov 2
Kurpilyanskiy 3
Leiserson undefined
Oparin 1
PP 3
QQ 4
RR 3
Rivest undefined
SS 3
Samsonov 2
TT 2
Toropov 1