These four frames are "stretched" into five by exploiting the interlaced nature of 60 Hz video. For every frame, there are actually two incomplete images or "fields", one for the odd-numbered lines of the image, and one for the even-numbered lines. There are, therefore, ten fields for every four film frames, which are called "A", "B", "C", and "D". The telecine alternately places A frame across two fields, B frame across three fields, C frame across two fields and D frame across three fields. This can be written as A-A-B-B-B-C-C-D-D-D or 2-3-2-3 or simply 2–3. The cycle repeats itself completely after four film frames have been exposed: