local mfl, mce = math.floor, math.ceil
local mmi, mma = math.min, math.max
local pow2 = {1}
for i = 2, 28 do pow2[i] = pow2[i - 1] * 2 end
local SegTree = {}
SegTree.updateAll = function(self)
  for i = self.stagenum - 1, 1, -1 do
    local cnt = pow2[i]
    for j = 0, cnt - 1 do
      self.stage[cnt + j] = self.func(self.stage[(cnt + j) * 2], self.stage[(cnt + j) * 2 + 1])
    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
  end
  self.stagenum = stagenum
  for i = 1, mul * 2 - 1 do self.stage[i] = emptyvalue end
  for i = 1, n do self.stage[mul + i - 1] = i end
  self:updateAll()
end
SegTree.update = function(self, idx)
  idx = idx + pow2[self.stagenum] - 1
  for i = self.stagenum - 1, 1, -1 do
    local dst = mfl(idx / 2)
    local rem = dst * 4 + 1 - idx
    self.stage[dst] = self.func(self.stage[idx], self.stage[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 h, w, k = io.read("*n", "*n", "*n")
local inf = h * w * k + 1
local x1, y1 = io.read("*n", "*n")
local sidx = (x1 - 1) * w + y1
local x2, y2 = io.read("*n", "*n", "*l")
local tidx = (x2 - 1) * w + y2
local len = {}
local asked = {}
for i = 1, h do
  local s = io.read()
  for j = 1, w do
    local idx = (i - 1) * w + j
    local f = s:sub(j, j) ~= "."
    for k = -3, 0 do
      len[idx * 4 + k] = inf
      asked[idx * 4 + k] = f
    end
  end
end
len[sidx * 4 - 3] = 0
len[sidx * 4 - 2] = 0
len[sidx * 4 - 1] = 0
len[sidx * 4] = 0

local n = h * w * 4
asked[n + 1] = true

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

local st = SegTree.new(n, mergefunc, n + 1)

local function walk(src, dst, cost)
  if not asked[dst] and len[src] + cost < len[dst] then
    len[dst] = len[src] + cost
    st:update(dst)
  end
end

for i = 1, n do
  local src = st.stage[1]
  if asked[src] then break end
  asked[src] = true
  st:update(src)
  local idx = mce(src / 4)

  local l = len[src]
  local z = mce(l / k) * k - l
  if src % 4 == 1 then
    -- to left
    if 1 < w and idx % w ~= 1 then
      walk(src, src - 4, 1)
    end
    walk(src, src + 1, z)
    walk(src, src + 2, z)
    walk(src, src + 3, z)
  elseif src % 4 == 2 then
    -- to right
    if 1 < w and idx % w ~= 0 then
      walk(src, src + 4, 1)
    end
    walk(src, src - 1, z)
    walk(src, src + 1, z)
    walk(src, src + 2, z)
  elseif src % 4 == 3 then
    -- to up
    if w < idx then
      walk(src, src - 4 * w, 1)
    end
    walk(src, src - 2, z)
    walk(src, src - 1, z)
    walk(src, src + 1, z)
  else
    -- to down
    if idx <= (h - 1) * w then
      walk(src, src + 4 * w, 1)
    end
    walk(src, src - 3, z)
    walk(src, src - 2, z)
    walk(src, src - 1, z)
  end
end

local ret = mmi(len[tidx * 4 - 3], len[tidx * 4 - 2], len[tidx * 4 - 1], len[tidx * 4])
if inf <= ret then
  print(-1)
else
  local l = mce(ret / k)
  print(l)
end
