# The four loops in the previous version have been factored
# out into a general function for entering positive numbers.
# Parameter Message will be passed the string specific to the
# desired value.

def Distance(X1,Y1,X2,Y2):
    DeltaX = X2 - X1
    DeltaY = Y2 - Y1
    return sqrt(DeltaX*DeltaX + DeltaY*DeltaY)

def GetAPositive (Message):
    N = input(Message)
    while (N < 0):
        print "This value is bogus"
        N = input(Message)
    return N
    
def Main():
    A1 = GetAPositive("Enter X1 --- ")
    B1 = GetAPositive("Enter Y1 --- ")
    A2 = GetAPositive("Enter X2 --- ")
    B2 = GetAPositive("Enter Y2 --- ")
    print Distance(A1,B1,A2,B2)
    return