4025
Triple 3-input NOR gates.

    +----------+             +---------------+       _____
 1A |1  +--+ 14| VCC         | A | B | C |/Y |  /Y = A+B+C
 1B |2       13| 3C          |---+---+---+---|
 2A |3       12| 3B          | 0 | 0 | 0 | 1 |
 2B |4  4025 11| 3A          | 0 | 0 | 1 | 0 |
 2C |5       10| /3Y         | 0 | 1 | X | 0 |
/2Y |6        9| /1Y         | 1 | X | X | 0 |
GND |7        8| 1C          +---------------+
    +----------+

[This information is part of the GIICM]