Problem 4. Suppose there is an array of length n. It contains values in the range of [1 . . . n 1]. However, exactly one value out of {1, . . . , n 1} is missing from this array. Find this missing number as efficiently as possible when the array is sorted such that the value stored at index 1 < value at index 2 < . . . < value at index n. Write pseudo code to find the missing number. Analyze the algorithm exactly.