Jigui got this letter one day.
This letter began in England, travelled around the world once a year, and brought luck to everyone who received it. Now it has reached you. You must solve the problem below within 12 hours and send seven copies of this letter, this one included, to people who need luck. Copying is allowed. (...) The number written on this letter is m. Find the smallest positive integer n such that n≡a−1(moda) for every natural number a with 2≤a≤m.
Jigui read the letter all the way to the end by accident and has felt uneasy ever since, because the problem is still unsolved. Solve it for Jigui.