The oncology unit of Kansas General Hospital employs 30 registered nurses who provide nursing care in the morning, afternoon, and night shifts. Each shift needs to have 2 nurses, each shift needs to have one experienced and one novice nurse. A nurse can not work more than 2 consecutive shifts. Each nurse has the same number of working shifts. Every nurse needs to have the same amount of shifts during a month. Formulate an integer program that minimizes the number of nurses in each shift.