Modify Lead Qualification Process in Microsoft Dynamics CRM 2015 online

i want create only account record while clicking  Qualify button on the lead entity. i am using below code and register in prevalidation and tried in preoperation also.

plugin message=QualifyLead ,primary entity=lead.

i am not getting error.but this code  if (((OptionSetValue)context.InputParameters["Status"]).Value == 3) coming -1 . 

if (((OptionSetValue)context.InputParameters["Status"]).Value == 3) // 
{
context.InputParameters["CreateAccount"] = true;
context.InputParameters["CreateOpportunity"] = false;
context.InputParameters["CreateContact"] = false;

}