ex. 18と12の最大公約数を求める x / y 18 / 12 = 1 ... 6 12 / 6 = 2 ... 0 A . 6 var x = 18; var y = 12; while (x % y != 0) { var prevx = x; x = y; y = prevx % y; } System.Console.WriteLine(y);