Sudoku sometimes spelled Su Doku is a placement puzzle also known as Number Place in the United States. The aim of the puzzle is to enter a numeral from 1 through 9 in each cell of a grid most frequently a 9X9 grid made up of 3X3 subgrids (called regions) starting with various numerals given in some cells (the givens). Each row column and region must contain only one instance of each numeral. Completing the puzzle requires patience and logical ability. Its grid layout is reminiscent of other newspaper puzzles like crosswords and chess problems. The puzzle initially became popular in Japan in 1986 and attained international popularity in 2005. The word Sudoku means numbers singly in Japanese. The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are absolutely irrelevant. Any set of distinct symbols will do; letters shapes or colours may be used without altering the rules. The attraction of the puzzle is that the completion rules are simple yet the line of reasoning required to reach the completion may be difficult.