(C-a SPC, C-a n, C-a C-n)
Switch to the next window. This command can be used repeatedly to cycle through the list of windows. (On some terminals, C-SPC generates a NUL character, so you must release the control key before pressing space.)
(C-a p, C-a C-p, C-a C-h, C-a Backspace)
Switch to the previous window (the opposite of C-a n).