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Problem Bank · inv-2

Invariants & Monovariants · Invariant quantitiesOlympiad classic●●●●○ 8/10~8 min⏱ 0:00
The numbers 1,2,…,101, 2, \ldots, 10 are on a board. A move erases two numbers a,ba, b and writes a+b+aba + b + ab. After nine moves one number remains. What are its last three digits?
invariantproduct