If S={θ∈[−π,π]:cosθcos5θ2=cos7θcos7θ2}S = \{ \theta \in [-\pi, \pi] : \cos \theta \cos \dfrac{5\theta}{2} = \cos 7\theta \cos \dfrac{7\theta}{2} \}S={θ∈[−π,π]:cosθcos25θ=cos7θcos27θ}, then n(S)n(S)n(S) is equal to ________.