a,b,t = STDIN.read.chomp.split(" ")

tot_time = t.to_f + 0.5
time_span = a.to_f
buisquets_per_span = b.to_i

counter = 1
tot_buisquets = 0
time_passed = 0
while time_span < tot_time
  tot_buisquets += buisquets_per_span
  time_passed += time_span
  time_span = time_span * counter
  counter += 1
end
puts tot_buisquets
