Otherwise we get the error:

Error{0}> l-f+1>=0
Error{1}> l-f+1>=0
Error{0}>
Error{0}> *** Runtime-error ******************
Error{0}>     Assertion: l-f+1>=0, failed in /home/matthias/Documents/projects/OPAL/src/ippl/src/Index/IndexInlines.h, line       57.

modified:   src/Classic/Algorithms/AmrPartBunch.cpp
modified:   src/Classic/Algorithms/AmrPartBunch.h