Math Help - Homework Prob, physics related

A stone is tossed down with a speed of 8m/s from the edge of a cliff 63 m high. how long will it take to hit the foot of the cliff?

vi= 8
a= 9.8
s= 63

i dont know the physics equation for a item being tossed from a cliff.

The stone is subject to gravity. If its initial position height is h(0) and its initial speed v(0), then the equation is:

.

With g = 9.81 m/s² and h choosen positive in the upwards direction.