Find the number of distinct values of this expression:
⌊N/4⌋ - ⌊N/7⌋ - ⌊N/14⌋ - ⌊N/28⌋

Notes:
1) ⌊x⌋ is the floor of x, which is the greatest integer less than or equal to x.
2) Adapted from a problem appearing in Singapore Mathematical Olympiad, Junior 2022.