python

Your favourite public transport company LS (we cannot use their real name here, so we permuted the letters) wants to change signs on all bus stops. Some bus stops have quite a few buses that stop there and listing all the buses takes space. However, if for example buses 141, 142, 143 stop there, we can write 141-143 instead and this saves space. Note that just for two buses this does not save space. You are given a list of buses that stop at a bus stop. What is the shortest representation of this list? Input The first line of the input contains one integer N, 1