How to count number of consistency checks in CSP backtracking algorithm?

Function BACKTRACKING-SEARCH(csp)returns a solution,or failure return BACKTRACK({},csp) Function BACKTRACK(assignment, csp) returns a solution, or failure begin if assignment is complete then return assignment  var = SELECT-UNASSIGNED-VARIABLE(VARIABLES[csp],assignment,csp)  for each value in ORDER-DOMAIN-VALUES(var, assignment, csp) do  if value is consistent with assignment then  add {var = value} to assignment  Result ←BACKTRACK(assignment,csp) If Result ≠ failure then return Result Remove {var=value} and inferences from assignment End if End for Return failure end 

This is the algorithm of backtracking algorithm.How to add number of consistency checks in this algorithm?