#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef vector<double> vd;
typedef vector<vd> vdd;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_print(x...) cerr << "line " << __LINE__ << " : "; debug_print_in(x);

template <typename First>
void debug_print_in(First first){
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_print_in(First first, Rest... rest){
  cerr << first << " ";
  debug_print_in(rest...);
  return;
}

void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

template <typename First>
void OUT(First first){
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template<class t, class u> void chmax(t&a,u b){if(a<b)a=b;};
template<class t, class u> void chmin(t&a,u b){if(a>b)a=b;};
int popcount(int t){return __builtin_popcount(t);} //GCC
int popcount(ll t){return __builtin_popcountll(t);} //GCC

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cerr << VEC[i] << " ";
  }

  cerr << endl;
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i,MAT.size()){
    REP(j,MAT[i].size()){
      cerr << MAT[i][j] << " ";
    }
    cerr << endl;
  }
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  ll H, W, K;
  IN(H,W,K);
  ll x1, y1, x2, y2;
  IN(x1,y1,x2,y2);
  x1--; y1--; x2--; y2--;

  vector<vector<char>> c(H,vector<char>(W));
  REP(i,H){
    REP(j,W){
      IN(c[i][j]);
    }
  }

  vvll state(H, vll(W, INFLL));
  priority_queue<pair<ll, pll>> que;
  que.push(make_pair(0, make_pair(x1, y1)));
  state[x1][y1] = 0;

  while(que.size()>0){
    pair<ll, pll> tmp = que.top(); que.pop();
    ll count = -tmp.first;
    ll x = tmp.second.first;
    ll y = tmp.second.second;

    bool flag = false;
    if(x<H-1){
      if(state[x+1][y]>state[x][y]){

        for(ll ix=x+1; ix<x+K+1; ++ix){
          if(ix>=H) break;
          if(c[ix][y]=='@') break;
          if(state[ix][y]>count+1){
            state[ix][y] = count+1;
            que.push(make_pair(-count-1, make_pair(ix, y)));
          }
        }
      }
    }
    if(x>0){
      if(state[x-1][y]>state[x][y]){

        for(ll ix=x-1; ix>x-K-1; --ix){
          if(ix<0) break;
          if(c[ix][y]=='@') break;
          if(state[ix][y]>count+1){
            state[ix][y] = count+1;
            que.push(make_pair(-count-1, make_pair(ix, y)));
          }
        }
      }
    }
    if(y<W-1){
      if(state[x][y+1]>state[x][y]){

        for(ll iy=y+1; iy<y+K+1; ++iy){
          if(iy>=W) break;
          if(c[x][iy]=='@') break;
          if(state[x][iy]>count+1){
            state[x][iy] = count+1;
            que.push(make_pair(-count-1, make_pair(x, iy)));
          }
        }
      }
    }
    if(y>0){
      if(state[x][y-1]>state[x][y]){

        for(ll iy=y-1; iy>y-K-1; --iy){
          if(iy<0) break;
          if(c[x][iy]=='@') break;
          if(state[x][iy]>count+1){
            state[x][iy] = count+1;
            que.push(make_pair(-count-1, make_pair(x, iy)));
          }
        }
      }
    }
  }

  if(state[x2][y2]==INFLL){
    OUT(-1);
  }else{
    OUT(state[x2][y2]);
  }

  return 0;
}

Measured memory_bytes: 19896