When an emergency arises in Paris or you want to report a problem to the police, dial "17". Today a security guard at the Banque de France helped me after an incident at the BNP Paribas Beaumarchais, Bastille. After speaking with the police on the guard's phone, I noticed the number on his screen "17". I will never forget that number and used it about an hour later. By coincidence the same three teenagers who hassled me earlier at the ATM inside the BNP Paribas were leaving the line one metro train the same time as I walked off. I dialed "17".