  All one-massless-loop Feynman diagrams could be written like a linear
combination of scalar boxes, triangles an bubbles in $n$ dimensions plus
rational terms. However, the four-point scalar integrals in $n+2$ dimensions
are free of infrared divergences. We are going to change the dimensions of the
scalar boxes $n \to n+2$ and the using of this degree of freedom to simplify
the computation of coefficients of the decomposition.
