do
  local function busyloop(final_ctr)
     final_ctr = final_ctr - final_ctr%1
     local ctr, prev_ms, ms0, ctr0 = 0
     while ctr ~= final_ctr do
        local ms = GetRunningTime()
        if prev_ms and ms ~= prev_ms then
           if not ms0 then
              ms0, ctr0 = ms, ctr
           elseif final_ctr < 0 and ms - ms0 > 500 then
              return (ctr - ctr0) / (ms - ms0)
           end
        end
        prev_ms = ms
        ctr = ctr + 1
     end
  end
  local coefficient = busyloop(-1)
  function FastSleep(ms)
     return busyloop(ms * coefficient)
  end
end