Reduce to One

You have become good friends with Chef. Right now, Chef is busy in the kitchen, so he asked you to solve a problem for him. Consider a list of integers $L$. Initially, $L$ contains the integers $1$ through $N$, each of them exactly once (but it may contain multiple copies of some integers later). The order of elements in $L$ is not important. You should perform the following operation $N-1$ tim