que devuelve la distancia al origen del punto (x,y).
Entrada
La entrada consiste en dos reales.
Observación
Sólo tenéis que enviar el procedimiento requerido;
el programa principal será ignorado.
About statements
The official statement of a problem is always the one
in the PDF document. The HTML version of the statement
is also given to help you, but may contain some content
that is not well displayed. In case of doubt, always use the PDF.