You are given a number , in how many different ways you can write that number in alphabetical form . eg n = 121 Different ways to write 121 are : (1)(2)(1) , (1)(21), (12)(1) [la] , So the ans for this example is 3. how can we solve this problem ?

You are provided with coins of denominations "a" and "b". You are required to find the least value of n, such that all currency values greater than or equal to n can be made using any number of coins of denomination "a" and "b" and in any order. If no such number exists, print "-1" in that case. how can i solve this question ?