Seems Easy?

Number Theory Level 3

Consider the set $A$ of numbers ${1,\frac{1}{2},\frac{1}{3},.....,\frac{1}{2012}}$ . We delete two of them say $a$ and $b$ and in their place we put only one number $a+b+ab$ . After performing the operation 2011 times what is the number that is left over.

Note- It's an old NMTC Junior level problem