1. Ilya takes a triplet of numbers and transforms it according to the rule: at each step, each number changes to the sum of the other two. What is the difference between the largest and the smallest numbers in the triplet after 1989 applications of this rule, if the initial triplet of numbers was $\{70 ; 61 ; 20\}$? If the question of the problem allows for multiple answers, then specify all of them in the form of a set.