# Find the first non-consecutive number
# Your task is to find the first element of an array that is not consecutive.
# By not consecutive we mean not exactly 1 larger than the previous element of the array.
# E.g. If we have an array [1,2,3,4,6,7,8] then 1 then 2 then 3 then 4 are all consecutive but 6 is not, 
# so that's the first non-consecutive number.
# If the whole array is consecutive then return null2.
# The array will always have at least 2 elements1 and all elements will be numbers. 
# The numbers will also all be unique and in ascending order. 
# The numbers could be positive or negative and the first non-consecutive could be either too!
# 1 Can you write a solution that will return null2 for both [] and [ x ] though? (This is an empty array and one with 
# a single number and is not tested for, but you can write your own example test. )


def first_non_consecutive(arr):
    for i,j in enumerate(arr,arr[0]):
        if i!=j:
            return j
arr=[1,2,3,4,6,7,8]
print(first_non_consecutive(arr))
