import math
def resolve():
    A, B, H, M = map(int, input().split())
    #短針が1時間で進む角度 30c
    deg_H = 360/12
    # 長針が1分間で進む角度 6c
    deg_M = 360/60

    hr = deg_H*H + (deg_H/60)*M
    mr = deg_M*M
    deg = abs(hr-mr)
    if deg>180:
        deg = 360- deg

    # 角度をラジアンに直す
    red = (deg/180)*math.pi
    ans = math.sqrt(A*A + B*B - 2*A*B*math.cos(red))
    print(ans)

if __name__ == "__main__":
    resolve()
