You are given an input string that controls the movement of a robot, $"$F$"$ means take a step forward, $"$L$"$ means turn $90$ degrees to the left and

$"$R$"$ means turn $90$ degrees to the right. E$.$g$."$FLF$"$ moves the robot one step forward, then turns it left by $90$ degrees, then moves the robot one step forward. Write a function that returns the minimum number of commands that the robot needs to return to its starting

point after following all the input commands. You should ignore any characters that are not capital F$,$ L$,$ or R$.$ Hint: you may wish to track the robots position using $($X$,$Y$)$ coordinates, assuming it starts at $(0,0).$

For example:

$*"$RF$"$ returns $3($robot must turn twice and move forward one step $($eg$."$RRF$")$

$*"$LFRFRFR$"$ returns $1($robot must step forward to return$)$

$*"$FxLxLxFx$"$ returns $0($robot is already back at its starting point$)$

$*[$execution time limit$]4$ seconds $($js$)$

$*[$memory limit$]1$ GB

$*[$input$]$ string directions$$The directions for the robot

$*[$output$]$ integer