~助詞+数量      => Corresponds to the verb...of quantity N5
Quantity
最中に => while; during; in the middle of ~ N3
〜がさいご(が最後) => if you do... negative result N1
Decisive (resolute decision)
[最中「さいちゅう」] => In the middle of A N3
Time, Situation
たが[最後「さいご」] => Once A occurs, B happens N1
Information, Report