Model the following puzzle into a constraint satisfaction problem. Each character in the following diagram represents a single digit and different characters represent different value. For example, SEND represents a number with 4 digits. The most significant digits are not equal to zero. You may use =, != (not equal), and arithmetic expression in your modeling. Find the value of each character, using the backtracking algorithm together with constraint propagation methods.

SE ND

+ MORE

MONEY

In your model, you should give variables and domain as well as the constraints.