#include <bits/stdc++.h>
#ifdef LOCAL_DEBUG
#define DEBUG 1
#define CERR if(DEBUG) cerr
#define MACRO(_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,NAME,...) NAME
#define pr(...) CERR<<MACRO(__VA_ARGS__,pr10,pr9,pr8,pr7,pr6,pr5,pr4,pr3,pr2,pr1)(__VA_ARGS__)<<endl
#define pr1(a) (#a)<<"="<<(a)<<" "
#define pr2(a,b) pr1(a)<<pr1(b)
#define pr3(a,b,c) pr1(a)<<pr2(b,c)
#define pr4(a,b,c,d) pr1(a)<<pr3(b,c,d)
#define pr5(a,b,c,d,e) pr1(a)<<pr4(b,c,d,e)
#define pr6(a,b,c,d,e,f) pr1(a)<<pr5(b,c,d,e,f)
#define pr7(a,b,c,d,e,f,g) pr1(a)<<pr6(b,c,d,e,f,g)
#define pr8(a,b,c,d,e,f,g,h) pr1(a)<<pr7(b,c,d,e,f,g,h)
#define pr9(a,b,c,d,e,f,g,h,i) pr1(a)<<pr8(b,c,d,e,f,g,h,i)
#define pr10(a,b,c,d,e,f,g,h,i,j) pr1(a)<<pr9(b,c,d,e,f,g,h,i,j)
#define prArr(a){CERR<<(#a)<<"={";int i=0;for(auto t:(a))CERR<<(i++?", ":"")<<t;CERR<<"}"<<endl;}
#else
#define DEBUG 0
#define pr(...)
#define prArr(a)
#endif
using namespace std;
using Int = long long;
using _int = int;
using ll = long long;
using Double = long double;
const Int INF = (1LL<<60)+1e9; // ~ 1.15 * 1e18
const Int mod = (1e9)+7;
const Double EPS = 1e-8;
const Double PI = 6.0 * asin((Double)0.5);
using P = pair<Int,Int>;
template<class T> T Max(T &a,T b){return a=max(a,b);}
template<class T> T Min(T &a,T b){return a=min(a,b);}
template<class T1, class T2> ostream& operator<<(ostream& o,pair<T1,T2> p){return o<<"("<<p.first<<","<<p.second<<")";}
template<class T1, class T2, class T3> ostream& operator<<(ostream& o,tuple<T1,T2,T3> t){return o<<"("<<get<0>(t)<<","<<get<1>(t)<<","<<get<2>(t)<<")";}
template<class T1, class T2> istream& operator>>(istream& i,pair<T1,T2> &p){return i>>p.first>>p.second;}
template<class T> ostream& operator<<(ostream& o,vector<T> a){Int i=0;for(T t:a)o<<(i++?" ":"")<<t;return o;}
template<class T> istream& operator>>(istream& i,vector<T> &a){for(T &t:a)i>>t;return i;}
//INSERT ABOVE HERE
template<typename dtype>
class RMQ{
public:
  Int n,n_;
  vector<dtype> dat;
  Int toMax;
  dtype initValue;/*範囲外のときに返す値*/
  //初期化
  RMQ(){n=-1;}
  RMQ(Int n_, Int toMax, dtype initValue):
    n_(n_),toMax(toMax), initValue(initValue){
    n=1;
    while(n<n_)n*=2;
    dat.resize(2*n-1,initValue);
  }

  inline dtype merge(dtype a,dtype b){return toMax? max(a, b):min(a, b); }

  //k番目の値をaに変更
  void update(Int k,dtype a){
    k+=n-1;
    dat[k]=a;
    while(k>0){
      k=(k-1)/2;
      dat[k]=merge(dat[k*2+1],dat[k*2+2]);
    }
  }

  dtype dfs(Int a,Int b,Int k,Int l,Int r){
    if(r<=a||b<=l)return initValue;
    if(a<=l&&r<=b)return dat[k];
    dtype vl = dfs(a,b,k*2+1,l,(l+r)/2);
    dtype vr = dfs(a,b,k*2+2,(l+r)/2,r);
    return merge(vl,vr);
  }

  //[a,b)の最小値を求める
  dtype get(Int a,Int b){
    assert(a <= b), assert(a <= n_ && b <= n_), assert(a >= 0 && a >= 0);
    return dfs(a,b,0,0,n);
  }
};

Int H, W, K;
vector<RMQ<P> > segX;
vector<RMQ<P> > segY;
vector<vector<Int> > X;
vector<vector<Int> > Y;
vector<string> mp;
Int sx, sy, gx, gy;
Int bfs(){
  queue<P> Q;
  Q.push(P(sy, sx));
  vector<vector<Int> > D(H, vector<Int>(W, INF));
  D[sy][sx] = 0;
  segX[sy].update(sx, P(0, sx));
  segY[sx].update(sy, P(0, sy));

  while(!Q.empty()){
    Int y, x; tie(y, x) = Q.front(); Q.pop();
    Int cost = D[y][x];
    if(mp[y][x] == '@') continue;
    //pr(y, x, cost);
    if(y == gy && x == gx) return cost;
    while(1){
      Int l = *(--lower_bound(X[y].begin(), X[y].end(), x));
      Int r = *(lower_bound(X[y].begin(), X[y].end(), x));
      auto p = segX[y].get(max<Int>(l + 1, x - K), min<Int>(r, x + K + 1));
      if(p.first <= cost + 1) break;
      //pr("x", l, r, p);
      Int ny = y;
      Int nx = p.second;
      Q.push(P(ny, nx));
      D[ny][nx] = cost + 1;
      segX[y].update(nx, P(cost + 1, nx));
      segY[nx].update(y, P(cost + 1, y));
    }
    while(1){
      Int l = *(--lower_bound(Y[x].begin(), Y[x].end(), y));
      Int r = *(lower_bound(Y[x].begin(), Y[x].end(), y));
      auto p = segY[x].get(max<Int>(l + 1, y - K), min<Int>(r, y + K + 1));
      //pr("y", l, r, p);
      if(p.first <= cost + 1) break;
      Int ny = p.second;
      Int nx = x;
      Q.push(P(ny, nx));
      D[ny][nx] = cost + 1;
      segY[x].update(ny, P(cost + 1, ny));
      segX[ny].update(x, P(cost + 1, x));
    }
  }
  return -1;
}

signed main(){
  srand((unsigned)time(NULL));
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(12);

  cin>>H>>W>>K;
  segX.resize(H, RMQ<P>(W, 1, P(-INF, -INF)));
  segY.resize(W, RMQ<P>(H, 1, P(-INF, -INF)));

  for(Int i=0;i<H;i++)
    for(Int j=0;j<W;j++) segX[i].update(j, P(INF, j));

  for(Int i=0;i<W;i++)
    for(Int j=0;j<H;j++) segY[i].update(j, P(INF, j));


  cin>>sy>>sx>>gy>>gx; sx--, sy--, gx--, gy--;
  mp.resize(H);
  cin>>mp;

  X.resize(H);
  Y.resize(W);
  for(Int i=0;i<H;i++) X[i].push_back(-1), X[i].push_back(W);
  for(Int i=0;i<W;i++) Y[i].push_back(-1), Y[i].push_back(H);
  for(Int i=0;i<H;i++)
    for(Int j=0;j<W;j++){
      if(mp[i][j] != '@') continue;
      X[i].push_back(j);
      Y[j].push_back(i);
    }

  for(Int i=0;i<H;i++) sort(X[i].begin(), X[i].end());
  for(Int i=0;i<W;i++) sort(Y[i].begin(), Y[i].end());

  Int ans = bfs();
  cout<<ans<<endl;


  return 0;
}


Measured memory_bytes: 201568