Agáta wrote the twenty-digit number 12345678901234567890. Filip selected four digits from Agáta's number that were written immediately next to each other. He tried to write these four digits in different orders and eventually managed to form a pair of two-digit numbers, where the first was 1 greater than the second.

Which pairs of numbers could Filip have formed? Determine all possibilities.

(L. Růžičková)
In every quartet of digits that Filip could choose from Agáta's number, the digits are mutually different. The resulting two numbers, therefore, could not have the same digits in the tens place (and differ by 1 in the units place). These numbers, therefore, had to be of the form $* 9 \mathrm{a} * 0$, with the digits in the tens place differing by 1.

In Agáta's number, all possible quartets of consecutive digits, among which are 9 and 0, are:

$$
7890, \quad 8901, \quad 9012 .
$$

From the first quartet, Filip could form the numbers 79 and 80; from the second quartet, he could not form anything; from the third quartet, he could form the numbers 19 and 20.

Evaluation. 2 points for each suitable pair of numbers; 2 points for the quality of the commentary.