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 work(A,B,C,D):
    tmp0=A*D-B*C
    tmp1=a*D+d*A-b*C-c*B
    tmp2=a*d-b*c
    if (tmp0==0):
        if (tmp1==0 and tmp2==0):
            return 0
        elif (tmp1!=0):
            return abs(tmp2/tmp1)
    else:
        delta=tmp1*tmp1-tmp0*tmp2*4
        if (delta>=0):
            return abs((tmp1+delta**0.5)/(tmp0*2))
    return 1e18
    
a,b=map(int,input().strip().split())
c,d=map(int,input().strip().split())

ans=1e18
ans=min(ans,work(1,1,1,1))
ans=min(ans,work(1,1,1,-1))
ans=min(ans,work(1,1,-1,1))
ans=min(ans,work(1,1,-1,-1))
ans=min(ans,work(1,-1,1,1))
ans=min(ans,work(1,-1,1,-1))
ans=min(ans,work(1,-1,-1,1))
ans=min(ans,work(1,-1,-1,-1))
ans=min(ans,work(-1,1,1,1))
ans=min(ans,work(-1,1,1,-1))
ans=min(ans,work(-1,1,-1,1))
ans=min(ans,work(-1,1,-1,-1))
ans=min(ans,work(-1,-1,1,1))
ans=min(ans,work(-1,-1,1,-1))
ans=min(ans,work(-1,-1,-1,1))
ans=min(ans,work(-1,-1,-1,-1))
print("%.10f" % ans)
