Ten children—Anna, Bob, Charles, Don, Emily, Frank, Gina, Hank, Irene, and Jane—are comparing their heights.
Jane is taller than Don.
Hank and Irene are the same height and both are shorter than Don.
Irene is taller than Bob.
Both Anna and Emily are taller than Gina.
Both Charles and Frank are shorter than Gina.
What is the minimum number of different heights the ten children can have?