(Challenge) Connecting computers

Chef has decided to start a new software company, the company's building has N offices numbered from 0 to N-1 and there's a computer in each office. All offices' computers should be connected within a single network, so it's required to buy some ethernet cables and hubs. a cable connecting i-th office with j-th office has cost Ci,j also if the i-th office is connected with j other offices the