local mfl, mce = math.floor, math.ceil
local mmi, mma = math.min, math.max
local bls, brs = bit.lshift, bit.rshift
local SegTree = {}
SegTree.updateAll = function(self)
  for i = self.stagenum - 1, 1, -1 do
    local cnt = bls(1, i - 1)
    for j = 1, cnt do
      self.stage[i][j] = self.func(self.stage[i + 1][j * 2 - 1], self.stage[i + 1][j * 2])
    end
  end
end
SegTree.create = function(self, n, func, emptyvalue)
  self.func, self.emptyvalue = func, emptyvalue
  local stagenum, mul = 1, 1
  self.stage = {{}}
  while mul < n do
    mul, stagenum = mul * 2, stagenum + 1
    self.stage[stagenum] = {}
  end
  self.stagenum = stagenum
  self.left_stage = {}
  for i = 1, n do
    local sp, sz = 1, bls(1, stagenum - 1)
    while(i - 1) % sz ~= 0 do
      sp, sz = sp + 1, brs(sz, 1)
    end
    self.left_stage[i] = sp
  end
  self.sz_stage = {}
  local tmp, sp = 1, stagenum
  for i = 1, n do
    if tmp * 2 == i then tmp, sp = tmp * 2, sp - 1 end
    self.sz_stage[i] = sp
  end
  for i = 1, n do self.stage[stagenum][i] = i end
  for i = n + 1, mul do self.stage[stagenum][i] = emptyvalue end
  self:updateAll()
end
SegTree.getRange = function(self, left, right)
  if left == right then return self.stage[self.stagenum][left] end
  local stagenum = self.stagenum
  local ret = self.emptyvalue
  while left <= right do
    local stage = mma(self.left_stage[left], self.sz_stage[right - left + 1])
    local sz = bls(1, stagenum - stage)
    ret = self.func(ret, self.stage[stage][1 + brs(left - 1, stagenum - stage)])
    left = left + sz
  end
  return ret
end
SegTree.update = function(self, idx)
  for i = self.stagenum - 1, 1, -1 do
    local dst = brs(idx + 1, 1)
    local rem = dst * 4 - 1 - idx
    self.stage[i][dst] = self.func(self.stage[i + 1][idx], self.stage[i + 1][rem])
    idx = dst
  end
end
SegTree.new = function(n, func, emptyvalue)
  local obj = {}
  setmetatable(obj, {__index = SegTree})
  obj:create(n, func, emptyvalue)
  return obj
end

local n = io.read("*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n")
end
local b = {}
for i = 1, n do
  b[i] = io.read("*n")
end
local fixedcnt = 0
local fixed = {}
for i = 1, n do
  fixed[i] = a[i] == b[i]
  if fixed[i] then fixedcnt = fixedcnt + 1 end
end
fixed[n + 1] = true

local function mergefunc(x, y)
  if fixed[x] then return y
  elseif fixed[y] then return x
  else
    return b[x] < b[y] and y or x
  end
end

local cnt = 0
local st = SegTree.new(n, mergefunc, n + 1)
while true do
  local top = st.stage[1][1]
  if fixed[top] then break end
  local left = top - 1
  if left == 0 then left = n end
  local right = top + 1
  if right == n + 1 then right = 1 end
  local dec = b[left] + b[right]
  local declim1 = mce((b[top] - b[left]) / dec)
  local declim2 = mce((b[top] - b[right]) / dec)
  local declim3 = mce((b[top] - a[top]) / dec)
  local deccnt = mmi(declim1, declim2, declim3)
  deccnt = mma(deccnt, 1)
  b[top] = b[top] - dec * deccnt
  cnt = cnt + deccnt
  if b[top] < a[top] then
    break
  elseif b[top] == a[top] then
    fixed[top] = true
    fixedcnt = fixedcnt + 1
    if fixedcnt == n then break end
  end
  st:update(top)
end
print(fixedcnt == n and cnt or -1)


Measured memory_bytes: 14720