Your task is to construct a building which will be a pile of n cubes.
The cube at the bottom will have a volume of n^3, the cube above 
will have  volume of (n-1)^3 and so on until the top which will have a volume of 1^3.
You are given the total volume m of the building.
Being given m can you find the number n of cubes you will have to build?
The parameter of the function findNb `(find_nb, find-nb, findNb)` will be an integer m
and you have to return the integer n such as
n^3 + (n-1)^3 + ... + 1^3 = m
if such a n exists or -1 if there is no such n.
## Examples:
```
findNb(1071225) --> 45
findNb(91716553919377) --> -1
```
def find_nb(m):
    i,sum = 1,1
    while sum < m:
        i+=1
        sum+=i**3
    return i if m==sum else -1
def find_nb(m):
    i,sum = 1,1
    while sum < m:
        i+=1
        sum+=i**3
    return i if m==sum else -1