It now remains to construct a global (approximate) solution to the Schrödinger equation. For the wave function to be square-integrable, we must take only the exponentially decaying solution in the two classically forbidden regions. These must then "connect" properly through the turning points to the classically allowed region. For most values of "E", this matching procedure will not work: The function obtained by connecting the solution near formula_53 to the classically allowed region will not agree with the function obtained by connecting the solution near formula_54 to the classically allowed region. The requirement that the two functions agree imposes a condition on the energy "E", which will give an approximation to the exact quantum energy levels.