function [t,y] = euler (f, y0, a, b, h)
    n = round((b - a)/h);
    t(1) = a;
    y(1) = y0;
    for i = 1 : n
        y(i + 1) = y(i) + h*f(t(i), y(i));
        t(i + 1) = t(i) + h;
    end
end