Factorial of any number greater than 5 ends with a zero. For a larger number, the number of zeroes at the end constitute a large part of the number. If you can eliminate those zeroes it will help.
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Use else if statement. According to your code, if a=0 and b=0 then both the first and the second if statements will be executed. And the output will be
"There are no solutions"
"There is one...

You can clear the entire screen using the cleardevice() function and redraw the square in a loop with the new positions.