Arpa research Mexican wavethere n spectator stadium label 1 n they start mexican wave time 0 at time 1 spectator stand at time 2 second spectator stand at time k kth spectator stand at time k1 k1th spectator stand spectator sit at time k2 k2th spectator stand second spectator sit at time n nth spectator stand nkth spectator sit at time n1 n1kth spectator sit at time nk nth spectator sit Arpa want know spectator stand time t