A little problem (inspired by CodeChef) for the coffee break.

A friend give you an array of size n-1 integers and these integers are in the range of 1 to n. There are no duplicates in array, but one of the integers is missing. Write efficient code to find the missing integer.

• The first argument contains an integer n denoting the size of array
• The second argument contains n integers A1, A2, ..., AN denoting the elements of array.