Differential Equations

Let \int_\limits0^x \sqrt{1-\left(y^{\prime}(t)\right)^2} d t=\int_0^x y(t) d t, 0 \leq x \leq 3, y \geq 0, y(0)=0. Then at $x=2, y^{\prime \prime}+y+1$ is equal to