if you have a heap(either min or max) if we delete first element then it coll heapify . and it will take logn .
so delete 1st element ------------->logn
delete 2nd element------------->logn
;
;
delete ith element --------------> logn
logn +logn+logn.................(upto i)
logn(1+1+............................)
logn * i
i(logn)------> O(logn)