# Actual parameters need not have the same names as formal parameters.

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

def Main():
    A1 = input("Enter X1 --- ")
    B1 = input("Enter Y1 --- ")
    A2 = input("Enter X2 --- ")
    B2 = input("Enter Y2 --- ")
    print Distance(A1,B1,A2,B2)
    return