PUZZLE NO. 503
Fill in the grid so that every row, every column and every 3 x 3 box contains the numbers 1 through 9 only once. Each 3 x 3 box is outlined with a darker line. You already have a few numbers to get you started. Remember: you must not repeat the numbers 1 through 9 in the same line, column or 3 x 3 box.