local mfl, mce = math.floor, math.ceil
local mmi, mma = math.min, math.max
local a, b, t = io.read("*n", "*n", "*n")
local ret = 1000000007 * 2
if a < 100000 then
  for i = 0, a - 1 do
    local rem = t - b * i
    if 0 <= rem then
      local v = mce(rem / a) * a + b * i
      ret = mmi(ret, v)
    else
      ret = mmi(ret, b * i)
    end
  end
else
  for i = 0, 100000 do
    local rem = t - a * i
    if 0 <= rem then
      local v = mce(rem / b) * b + a * i
      ret = mmi(ret, v)
    else
      ret = mmi(ret, a * i)
    end
  end
end
print(ret)