A swimming pool is open for 7\dfrac127 ​2 ​ ​1 ​​ 7, start fraction, 1, divided by, 2, end fraction hours during a day. The pool keeps one lifeguard on duty at a time, and each lifeguard's shift is 1\dfrac121 ​2 ​ ​1 ​​ 1, start fraction, 1, divided by, 2, end fraction hours long. How many shifts are there per day?