AMO · 2027 · Grades 6-7 · Self-study SET 27 Question 5

Each of 10 cards displays two different symbols, one on the front and one on the back. The five symbols are $\clubsuit,\heartsuit,\spadesuit,\diamondsuit,\bullet$. The front of each card is shown. No two cards have the same unordered pair of symbols. What is the least number of cards you can turn over to ensure that $\bullet$ appears?



**Input:** Enter the integer only, without units.