Definition: In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Input: Kouichi Sakakibara:  I understand that I no longer exist for them . But , why they do this ?
Mei Misaki: It is a natural question . Do you remember the story about Misaki who died twenty - six years ago ?
Kouichi Sakakibara: Yes .
Mei Misaki: That 's what started it all . After that , the class three was close to death .
Kouichi Sakakibara: Death ?
Mei Misaki: First happened to the class three the following year to Misaki 's classmates graduation . Once it happens , once it begins , someone dies every month . Whether a student or someone in their family .
Kouichi Sakakibara: What is " It " ?
Mei Misaki: It 's when ... the number of students in the class is incremented by _ one _ .
Kouichi Sakakibara: Incremented ? Who ?
Mei Misaki: Nobody knows , they may never know who 's that extra one .
Kouichi Sakakibara: Extra one ?

number