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10-digit numbers with digits 1-3, written

Source: 1968 Leningrad Math Olympiad - Grade 8.6* asterisk problem

September 1, 2024
number theorycombinatoricsDigits

Problem Statement

All 1010-digit numbers consisting of digits 1,21, 2 and 33 are written one under the other. Each number has one more digit added to the right. 11, 22 or 33, and it turned out that to the number 111...11111. . . 11 added 11 to the number 222...22 222. . . 22 was assigned 22, and the number 333...33333. . . 33 was assigned 33. It is known that any two numbers that differ in all ten digits have different digits assigned to them. Prove that the assigned column of numbers matches with one of the ten columns written earlier.