How much money do I need to quit working?

no-work-posession.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-


def geometric_coeff(percentage, n):
    if percentage != 0:
        ratio = percentage / 100.0
        return float((1 + ratio) ** n - 1) / ratio
    else:
        return n


if __name__ == '__main__':
    years_to_live = int(input("Remaining lifespan in years: "))
    yearly_interest = float(input("Yearly interest in percent: "))
    yearly_inflation = float(input("Yearly inflation in percent: "))
    yearly_spending = int(input("Yearly spending you want: "))

    effective_interest = yearly_interest - yearly_inflation

    # approximate for lifespan > 100
    if years_to_live <= 100:
        posession_coeff = geometric_coeff(effective_interest, years_to_live)
        spending_coeff = geometric_coeff(yearly_inflation, years_to_live)
        coeff_ratio = spending_coeff / posession_coeff
        result = years_to_live * yearly_spending * coeff_ratio
        print("You need " + str(result) + " to live without working")
    else:
        coeff_ratio = float(yearly_inflation) / effective_interest
        result = years_to_live * yearly_spending * coeff_ratio
        print("You need approx. " + str(result) + " to live without working")