Dad bought a big cylindrical birthday cake for his daughter. The daughter cut the cake vertically into 22 pieces and distributed them to 22 children. The cuts are not necessarily equal in size. So at least the number of knives to cut is?
爸爸给女儿买了一个圆柱形的大生日蛋糕，女儿把蛋糕竖直方向切成22块分给22个小朋友，切成的大小不一定相等．那么至少需切的刀数为？
<result>7</result>