Or communicate... or both.

• If you have a problem in an application and there is more than one developer working on the project, be sure to clearly communicate who is working on the problem. Otherwise, you'll end up with two people writing the same code in the same place, duplicating the effort and wasting at least one person's time
  
• If you need more than one person working on the problem, make sure that they are working together, closely, to avoid the same problem
  
• If you need input from other resources, be sure that the entire team working on the problem is involved in those conversations or is at least given a summary of the conversation, so that you don't have to go back to the external resource over and over again, to get the same information