right away; without delay; immediately
Set phrase meaning to do something without waiting or hesitation; often used when someone acts promptly without needing to be told twice.
He got right to work without waiting around.
説明を聞くと、一二に及ばず承諾した。
Upon hearing the explanation, he agreed right away.
The phrase literally means 'without reaching one or two', implying that one acts before even counting to two. The exact origin is uncertain, but it is a traditional idiomatic expression.