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  CalcHEP uses the importing sampling algorithm 
for event generator. To realize it CalcHEP 
divides the phase volume on sub-cubes and finds 
a local maximum in each  sub-cube. This menu 
item specifies the number of these sub-cubes.
 The increase of this number  leads  to 
improvement of efficiency of event generator, 
but, from other side, to increase the time 
needed to prepare the generator.
