Cyrus is on an adventure to the deep unknown forest, in order to get the mysterious treasure box. After walking for a few days, he found out that a strange door was blocking his way, and there weren't any paths that Cyrus could take. Without choice, he could only try to open the door. There were some numbers on the door and strangely, there was a touch-sensing screen near the side of the door. It showed the alphabet, from A-Z. There were also 4 lines on top of the alphabet buttons. Cyrus pressed a random letter, and it appeared on the first line. He quickly found out that it was a password lock. He cleared the letters and started to look at the four numbers. They are 2, 5, 13 and 34. The question comes. What are the 4 letters? What is the password? Can you help Cyrus solve the problem?
p.s. you can go ask your math teacher for hints