c - Reverse Modulus Operator with given condition -

i have equation:

x^2 mod p = z ; 

p , z given. x,p , z positive integers , max value of x given (say m). p prime. how can calculate (multiple possible values) x when p , z known ?

update:

i found solution here:

https://math.stackexchange.com/questions/848062/reverse-modulus-operator-with-given-condition/848106#848106

if x^2 mod p = z
x^2 = n*p + z integer n
p , z known, substitute integer values n find x