Try this Out.
I hope this helps.
void Update(){
if (Input.GetMouseButtonDown(0)){
startPosition = Input.mousePosition;
}
if (Input.GetMouseButtonUp(0)){
float swipe = startPosition.x - Input.mousePosition.x;
}
if (swipe < 0)
{
print("LTR");
} else{
print("RTL");
}
}
}
}