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A. Olesya and Rodion time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Olesya loves numbers consisting of n digits, and Rodion only likes numbers that are divisible by t. Find some number that satisfies both of them. Your task is: given the n and t print an integer strictly larger than zero consisting of n digits that is divisible by t. If such number doesn’t exist, print - 1. Input

有若干个活动，第i个开始时间和结束时间是[Si,fi)，同一个教室安排的活动之间不能交叠，求要安排所有活动，最少需要几个教室？ 1第一行一个正整数n (n <= 10000)代表活动的个数。 2第二行到第(n + 1)行包含n个开始时间和结束时间。 3开始时间严格小于结束时间，并且时间都是非负整数，小于1000000000 输出 一行包含一个整数表示最少教室的个数。 输入示例

C. GCD Table time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output The GCD table G of size n × n for an array of positive integers a of length n is defined by formula Let us remind you that the greatest common divisor (GCD) of two positive integers x and y is the greatest integer that is divisor of both x and y, it is denoted as . For example, for array a = {4, 3, 6, 2} of length 4 the GCD table will look as follows: