In a small town the population is `p0 = 1000` at the beginning of a year. The population
regularly increases by `2 percent` per year and moreover `50` new inhabitants per year
come to live in the town. 
How many years does the town need to see its population
greater or equal to `p = 1200` inhabitants?
```
At the end of the first year there will be: 
1000 + 1000 * 0.02 + 50 => 1070 inhabitants
At the end of the 2nd year there will be: 
1070 + 1070 * 0.02 + 50 => 1141 inhabitants (number of inhabitants is an integer)
At the end of the 3rd year there will be:
1141 + 1141 * 0.02 + 50 => 1213
It will need 3 entire years.
```
More generally given parameters:
`p0, percent, aug (inhabitants coming or leaving each year), p (population to surpass)`
the function `nb_year` should return `n` number of entire years needed to
get a population greater or equal to `p`.
aug is an integer, percent a positive or null number, p0 and p are positive integers (> 0)
```
Examples:
nb_year(1500, 5, 100, 5000) -> 15
nb_year(1500000, 2.5, 10000, 2000000) -> 10
```
Note: Don't forget to convert the percent parameter as a percentage in the body of your function: if the parameter percent is 2 you have to convert it to 0.02.
def nb_year(population, percent, aug, target):
    year = 0
    while population < target:
        population += population * percent / 100. + aug
        year += 1
    return year
def nb_year(population, percent, aug, target):
    year = 0
    while population < target:
        population += population * percent / 100. + aug
        year += 1
    return year