Find the largest number equal to or less than given number N where all digits must be in increasing order.\ne.g, \n```\nInput : 573\nOutput: 569\n\nInput: 1234\nOutput: 1234\n```\n\nBrute force will be to decrease given number by 1 until digits are not in increasing order. What will be an optimal approach?

Find the largest number equal to or less than given number N where all digits must be in increasing order.\ne.g, \n\nInput : 573\nOutput: 569\n\nInput: 1234\nOu