Parsec to Planck

There are 2020 people standing in a circle numbered 1-2020. Whoever has the weapon kills the $n^{th}$ person in front of him and gives the weapon to the $n+1^{th}$ person in front, that is, if 1 has the weapon and no one is killed yet he kills $1+n$ and gives the weapon to $2+n$. Find out who is the last one to be alive. ###Input Format The only line of input contains the integer $n$.