### smallestChair 
from heapq import heapify, heappush, heappop
from typing import *
def f_gold(times: List[List[int]], targetFriend: int) -> int:
    n = len(times)
    h = list(range(n))
    heapify(h)
    for i in range(n):
        times[i].append(i)
    times.sort()
    busy = []
    for a, b, i in times:
        while busy and busy[0][0] <= a:
            heappush(h, heappop(busy)[1])
        c = heappop(h)
        if i == targetFriend:
            return c
        heappush(busy, (b, c))
    return -1