a, b, c = io.read("*n", "*n", "*n")
t = {}
if c <= b then
  if c % a == 0 then
    table.insert(t, math.floor(c / a))
  end
end
if (c + b) % a == 0 then
  table.insert(t, math.floor((c + b) / a))
end
if #t == 0 then
  print(-1)
else
  print(table.concat(t, "\n"))
end