A group of four letters.

The first letter order is: a, b, c, d ... so the next one is e.

The order of the second letter is: A, D, G, J ... The letter after it is the third letter after the previous letter, so the next letter is M,

In order, you can easily get the answer: emae.

Be calm when you meet something you can't. They all have hidden rules. It depends on whether you can find it! ! !