For a > 0, let ya(x) be the solution to the differential equation \(2\frac{d^2y}{dx^2}-\frac{dy}{dx}-y=0\) satisfying the conditions y(0) = 1, y'(0) = a. Then, the smallest value of a for which ya(x) has no critical points in ℝ equals ___________ (rounded off to the nearest integer).