n this method of playing, he first bets say $1;  if he loses
| it he bets $2;  if he loses that he bets $4;  if he loses that
| he bets $8;  if he then gains he has lost 1 + 2 + 4 = 7, and
| he has gained $1 more;  and no matter how many bets he loses,
| the first one he gains will make him $1 richer than he was in
| the beginning.  In that way, he will probably gain at first;
| but, at last, the time will come when the run of luck is so
| against him that he will not have money enough to double, and
| must