Balloon++

I hope you are enjoying the competition

We the authors (Diego Rangel, Francisco Arcos, Gabriel Duarte and Gustavo Policarpo), we are happy to be trying to solve our problems. For you who are beginner and do not leave the room without any balloon here is a challenge for you:

• This year the balloons have a spherical shape, according to the company that produces the balloons: "... for complex engineering reasons, this format is better (...)" will understand ...
• However this format makes the balloon use more helium gas and this caused a problem because the organizer had already bought a tank with L liters of gas before this novelty in the balloon market.

Knowing the radius of the balloon model and the amount of helium gas available, could you help the team by saying how many balloons can be filled completely?