'''
Created on Sep 12, 2017

@author: Susan
'''
def minutesNeeded (numCakes, capacity):
    if numCakes == 0:
        return 0
    if numCakes % capacity == 0:
        return numCakes/capacity * 10
    if numCakes <= capacity:
        return 10
    if (numCakes%capacity) /capacity <= 0.5:
        return numCakes/capacity * 10 +5
    # this may not be right
    return -1
    
    
if __name__ == '__main__':
    pass