function y = adams(ef, y0, h, a, b)
y(1) = y0;
n = (b - a) / h;
x = a : h : b;
for i = 1 : n
  y(i+1) = y(i) + h * feval(ef, x(i), y(i)); 
  y(i+1) = y(i) + h / 2 * (feval(ef, x(i), y(i)) + feval(ef, x(i+1), y(i+1)));
end