
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

    # if b*math.tan(math.pi/2-rad)>a:
    #     return (a*b - a*math.tan(rad)*a*1/2) *a
    # else:
    #     return (b*math.tan(rad/2-rad)*b*1/2)*a
    # print(a_sect, b_sect)
    return (sqr_a + tri_a) * 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 <= 0 and y - x >= -10 ** -7 :
            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()
