Flower-4 Sudoku

Flower-4 is a combination of four Sudoku grids with common blocks shaped like a flower. Each of these four puzzles cannot be solved separately; there is only one common solution.

Rules: Four regular 9×9 Sudoku grids have some blocks in common. The overlapping blocks are highlighted in different colours depending on the number of overlaps. None of these grids can be solved separately, but all of them together have a unique solution.
In each cell of the 9×9 grid, enter a number from the range 1–9. Each number must appear exactly once in each row, column, and block.