HMMT 二月 2008 · 冲刺赛 · 第 35 题

HMMT February 2008 — Guts Round — Problem 35

NUMB3RS. The RSA Factoring Challenge, which ended in 2007, challenged computational mathe- maticians to factor extremely large numbers that were the product of two prime numbers. The largest number successfully factored in this challenge was RSA-640, which has 193 decimal digits and carried a prize of $20 , 000. The next challenge number carried prize of$ 30 , 000, and contains N decimal digits. Your task is to submit a guess for N . Only the team(s) that have the closest guess(es) receives points. ⌈ ⌉ 20 If k teams all have the closest guesses, then each of them receives points. k

解析

NUMB3RS. The RSA Factoring Challenge, which ended in 2007, challenged computational mathe- maticians to factor extremely large numbers that were the product of two prime numbers. The largest number successfully factored in this challenge was RSA-640, which has 193 decimal digits and carried a prize of $20 , 000. The next challenge number carried prize of$ 30 , 000, and contains N decimal digits. Your task is to submit a guess for N . Only the team(s) that have the closest guess(es) receives points. ⌈ ⌉ 20 If k teams all have the closest guesses, then each of them receives points. k Answer: 212 For more information, see the Wikipedia entry at http://en.wikipedia.org/wiki/ RSA_Factoring_Challenge . RSA-640 was factored in November 2005, and the effort took approximately 30 2.2GHz-Opteron-CPU years over five months of calendar time.