你逐個數拎出嚟試，睇下俾二除唔除得開，跟住試三、五、七，逐個質數試，試到嗰個數嘅開方為止。
You take out the numbers one by one and try to see if they can be divided by two, and then try three, five, seven, and try the prime number one by one, until the square of that number is opened.