at once

adverbs

without delay or hesitation; with no time intervening
"he answered immediately"; "found an answer straightaway"; "an official accused of dishonesty should be suspended forthwith"; "Come here now!"
at once, directly, forthwith, immediately, instantly, like a shot, now, right away, straight off, straightaway
simultaneously
"he took three cookies at a time"
at a time, at once, at one time