The determinant of a matrix 2 × 2 is defined as follows:

A matrix is called degenerate if its determinant is equal to zero. 

The norm ||*A*|| of a matrix *A* is defined as a maximum of absolute values of its elements.

You are given a matrix <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/e78540a0de68f85833f82714a7141114b781276e.png" style="max-width: 100.0%;max-height: 100.0%;"/>. Consider any degenerate matrix *B* such that norm ||*A* - *B*|| is minimum possible. Determine ||*A* - *B*||.
The first line contains two integers *a* and *b* (|*a*|, |*b*| ≤ 10<sup class="upper-index">9</sup>), the elements of the first row of matrix *A*. 

The second line contains two integers *c* and *d* (|*c*|, |*d*| ≤ 10<sup class="upper-index">9</sup>) the elements of the second row of matrix *A*.
def calc_range(x, y, d):
    l1 = x - d
    r1 = x + d
    l2 = y - d
    r2 = y + d
    points = sorted([l1 * l2, l1 * r2, r1 * l2, r1 * r2])
    return points[0], points[3]

def main():
    a, b = map(int, input().split())
    c, d = map(int, input().split())
    l = 0.0
    r = 1e10
    for iter in range(100):
        m = (l + r) / 2.0
        minA, maxA = calc_range(a, d, m)
        minB, maxB = calc_range(b, c, m)
        if maxA < minB or maxB < minA:
            l = m
        else:
            r = m
    print(r)

if __name__ == "__main__":
    main()