Sum of 10's a pie

Geometry Level 3

$\arctan\left(\frac {1}{3} \right)+ \arctan\left(\frac {1}{4}\right) + \arctan\left(\frac {1}{5} \right)+ \arctan\left(\frac {1}{n} \right)= \frac {\pi}{4}$

Find the positive integer $n$ such that it satisfy the equation above.