[计] inverse discrete Fourier transform

lí sàn fù lǐ yè nì biàn huàn ㄌㄧˊ ㄙㄢˋ ㄈㄨˋ ㄌㄧˇ ㄧㄝˋ ㄋㄧˋ ㄅㄧㄢˋ ㄏㄨㄢˋ