Chopin, Etude C major Op. 10 No. 1, with fingerings for the left hand:
With these fingerings also pianists with smaller, weaker and less flexible hands may be able to play this etude and it's still difficult enough for the right hand.
Practise the exercises and the etude every day or every two or three days for 10 to 20 minutes. If you want to practise the etude more intensively, practise alternately the exercises and the etude and other, less difficult pieces.
An unusual exercise - play on a desk or on your thighs:
(or, if you really want to annoy your neighbours, play on the piano)
and play at the same time the etude in your head.