#This example may require extra memory.
file:=HapFile("data1XD3.pdb");
K:=ReadPDBfileAsPureCubicalComplex(file,5);;
K:=ContractedComplex(K);;
for i in [0..5] do
 Y:=RegularCWComplex(ContractedComplex(K));;
 Print(CriticalCells(Y),"\n");
 K:=PureComplexThickened(K);;
od; 
