import math
# Calculate amount of water that won't oveflow
def calc(a,b,deg): 
    
    rad = math.radians(deg)
    # deg90_in_rad = math.radians(90)
    # a_sect = a*math.sin(rad) - b*math.sin(deg90_in_rad - rad)
    # b_sect = b*math.sin(deg90_in_rad - rad) - a*math.sin(rad) # 縦と水の切片

    # if b_sect >= 0:
    #     sqr_a = a * b_sect 
    #     tri_a = (b-b_sect)*a*1/2  

    # else:
    #     sqr_a = 0
    #     tri_a = (a - a_sect) * b *1/2
    # total_area = (sqr_a + tri_a) 

    if b*math.tan(math.pi/2-rad) <= a:
        total_area = (b*math.tan(math.pi/2-rad)*b*1/2)
    if b*math.tan(math.pi/2-rad)>a:
        total_area = (a*b - a*math.tan(rad)*a*1/2)       

    return total_area * a

import bisect
def main():
    a, b, x = list(map(int, input().split()))

    left = 0
    right = 90
    deg = 45
    while True:
        y = calc(a, b, deg)
        if y - x >= -10 ** -7 and y - x <= 0:
            break
        if y > x:
            deg, left = (right+deg)/2, deg
        elif y < x:
            deg, right = (left+deg)/2, deg
    print(deg)

if __name__ == "__main__":
    main()
