Doesnt work, what do I need to change?

Code:#include <iostream> using namespace std; double U; double L = 0; double guess; double abs(int a,int b) { if ((a-b) < 0) { return (a-b)*-1; } else { return (a-b); } } double sqrt(double x) { if (x == 0 || x == 1) { return x; } else { guess = x/2; } while (abs((guess*guess)-x) != .0000000000000000001) if (guess*guess > x) { U = guess; guess = ((U - L)/2) + L; } else { L = guess; guess = ((U - L)/2) + L; } cout<<guess; }