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Senior Member
Posted 08 February 2013 - 06:44 AM
All numbers from 1 to 1966 are written on a blackboard.
You are allowed to erase any two numbers and write their difference instead.
Prove that repetition of that operation may not result in having only zeroes on the blackboard.
(Problem from Russian Math Olympiads. 6-th grade, 1966.)
Past prime, actually.
Advanced Member
Posted 08 February 2013 - 01:59 PM Best Answer
Senior Member
Posted 08 February 2013 - 10:13 PM
Spoiler for Solution
Nice. When at math competition, solve it like this and you have extra time to tackle other problems.
Past prime, actually.
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