Your task is to calculate ab mod 1337 where a is a positive integer and b is an extremely large positive integer given in the form of an array. Example 1: Input: a = 2, b = [3] Output: 8 Example 2: Input: a = 2, b = [1,0] Output: 1024 Example 3: Input: a = 1, b = [4,3,3,8,5,2] Output: 1 Example 4: Input: a = 2147483647, b = [2,0,0] Output: 1198 Constraints: 1 <= a <= 231 - 1 1 <= b.length <= 2000 0 <= b[i] <= 9 b doesn't contain leading zeros.