how do I search 1D array

[Mudda]

I have a 1D array of elements from 1 to 100. each number is repeated
more than once in the array. i want to search the index when a new
number is found for the first time in my array. if my array is
{1,1,1,2,2,2,2,3,3,3,3,3,4,4,5,5,5,5....} i want to find the index
when 1,2,3,4,5,.... are occured for the first time. when i use search
1D array function and put that in a loop and increment every time the
search element the index i am reading is always -1.