Microsoft Internship interview questions

After a phone screen I was invited to participate in an on-site interview for a summer internship. The process was a full day event 9am-5pm, and I actually ended up missing my return flight home from Redmond. I went through 4 interviews, where 1 was combined with a lunch interview. At the end I met with the hiring manager, where I made a silly mistake on a whiteboard problem because I was so exhausted. I found out 3 days later that I did not make the cut for the internship.