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Let us begin with a positive integer N and find the smallest positive integer which doesn't divide N. If we repeat the procedure with the resulting number, then again with the new result and so on, we will eventually obtain the number 2 (two). Let us define strength(N) as the length of the resulting sequence. For example, for N = 6 we obtain the sequence 6, 4, 3, 2 which consists of 4 numbers, thus strength(6) = 4. Given two positive integers A < B, calculate the sum of strengths of all integers between A and B (inclusive), that is, strength(A) + strength(A + 1) + ... + strength(B). |
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11 11 262 262 2329 2329 51690500 51690500 5169052 5169052 3029585029808980 |