Normal sudoku rules apply. Draw a closed loop that moves orthogonally or diagonally between the centres of no more than 23 cells. The loop passes through all boxes except box 5 (the shaded box). The digit 1 appears on the loop once, the digit in the circle appears on the loop twice, and every other digit N that appears anywhere on the loop appears on the loop N times. Adjacent digits on the loop are different and box borders divide the loop into regions of equal sums.