math.randomseed(os.time())

function Test()
  local S = math.random(100)
  local a = S ^ 0.5
  return a, S
end

function Sol(a)
  local S = a ^ 2
  return S
end

a, S_test = Test()
io.write('a = ', a, '\n')
S = Sol(a)
if not S or S ~= S_test then io.write('error\n') end
io.write('S = ', S, '\n')