you are the GREAT!!!
but need to do floor()
because the number of people cannot be fractional :)

nbYear(a, b, c, d) => a >= d ? 0 : 1 + nbYear((a + a*b/100 + c).floor(), b, c, d);

i tested this function against the simple while loop solution with 500.000 and bigger upper limit it is in fact less performant

Mindblowing

fucking genius you beat me

awesome recursion.

else if

Very well summarized! Although the keys are not necessary since "n" has no property.