Create an ellipse out of focal points and the length of a string connecting both points.

Input parameters:

1. Pl → Plane for ellipse.
2. F1 → First focal point of ellipse.
3. F2 → Second focal point of ellipse.
4. Ln → Total length of the two line segments making up the string.

Output parameters:

1. El → Ellipse from foci and string length.