Let  $S_1 \&S_2$ be the two foci of an ellipse and P be a point of the ellipse such that  $\angle S_{1}P{S}_2$ is a right angle. Area & perimeter of triangle $S_{1}P{S}_2$ be respectively 30 sq.units & 30 units. 
Let the Length of semi-major axis of the ellipse is  $\text{'}p\text{'}$ units and Distance between the foci is $\text{'}q\text{'}$  units and Eccentricity of the ellipse is  $\text{'}r\text{'}$. Then the value of  $[q-p+r]$ is ____, where $[.]$ denotes represents Greatest Integer Function.