title: Quadratic equation: TypeError: bad operand type for unary -: 'str'
body: <p>I´m new to Python and have been trying to code the quadratic equation, but i keep running into this error:
  TypeError: bad operand type for unary -: 'str'</p>
  <pre><code>def quad_gleichung():
  a = input('a:')
  b = input('b:')
  c = input('c:')
  
  x1 = int(-b + (b**2 - (4*a*c))**(0.5)) / (2*a)
  x2 = int(-b - (b**2 - (4*a*c))**(0.5)) / (2*a)
  
  
  print('Lösung 1:', x1)
  print('Lösung 2:', x2)
  
  quad_gleichung()
  </code></pre>
  <p>Can anyone please help me?</p>
  <p>Thanks!</p>