Let M be a smooth compact and simply-connected manifold with simplyconnected boundary ∂ M, r be a fixed odd natural number. We consider f , a C 1 self-map of M, preserving ∂ M. Under the assumption that the dimension of M is at least 4, we define an invariant D r ( f ; M, ∂ M) that is equal to the minimal number of r -periodic points for all maps preserving ∂ M and C 1 -homotopic to f . As an application, we give necessary and sufficient conditions for a reduction of a set of r -periodic points to one point in the C 1 -homotopy class.