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The basic backtracking algorithm provides a framework for solving problems using the backtracking technique. It follows a recursive approach to explore all possible solutions to a problem by creating a search tree. At each step, it makes a choice and proceeds to the next step until a solution is found or all possibilities have been exhausted.

The general structure of the basic backtracking algorithm can be defined using the following steps:

1. Define a backtrack function that takes the necessary parameters.
2. Check for the base case(s) that indicate a solution has been found.
3. Check for any constraints that need to be satisfied at the current step.
4. Make a choice to move to the next step.
5. Recursively call the backtrack function for the next step.
6. Undo the previous choice before backtracking to the previous step.

Let's fill in the blank for step 3. At step 3, we need to check for any ___ that need to be satisfied at the current step.