I remember long ago, when somebody wanted to emulate a small routine for adding big numbers, using a crowd of people as an arithmetic unit. The task was simple for everyone in the crowd. Like just add two given numbers from 0 to 9 and report the integer part of the result divided by 10 to the next one in the crowd and remember your result modulo 10.

The crowd was assembled of mathematicians. Still, at every attempt someone made an error, while adding 5 and 7 or something.