Logic Masters Deutschland e.V.

Rules
Normal sudoku rules apply.
Cells separated by a king's move cannot contain the same digit.
In this puzzle, there are exactly 15 "friendly" cells. A cell is "friendly" if it contains its row, column, or box number.
A "friendly" cell filled with the digit N must either be in row N-3, row N, or row N+3.
Additionally, there must be at least 3 "friendly" cells in column 1. The digits in those cells indicate the position of 1 in their row. The same is true in columns 5 and 9 for 5's and 9's respectively.

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