A robot is located in the upper-left corner of a 4×4 grid. The robot can move either up, down, left, or right, but cannot go to the same location twice. The robot is trying to reach the lower-right corner of the grid. Your task is to find out the number of unique ways to reach the destination.

There is no input for this program.

Print out the number of unique ways for the robot to reach its destination. The number should be printed out as an integer ≥0.