#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <string>
#include <math.h>
#include <iomanip>
#include <limits>
#include <list>
#include <queue>
#include <tuple>
#include <map>
#include <stack>
#include <set>
#include <bitset>
#include <functional>
#include <cassert>
using namespace std;
#define fast_io ios_base::sync_with_stdio (false) ; cin.tie(0) ; cout.tie(0) ;
#define ll long long int
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define reps(i,n) for(int i=1; i<=(int)(n); i++)
#define REP(i,n) for(int i=n-1; i>=0; i--)
#define REPS(i,n) for(int i=n; i>0; i--)
#define MOD (long long int)(1e9+7)
#define INF (int)(1e9)
#define LINF (long long int)(1e18)
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
#define all(v) v.begin(), v.end()
typedef pair<int, int> Pii;
typedef pair<ll, ll> Pll;

ll mpow(ll a, ll b){
  if(b==0) return 1;
  else if(b%2==0){ll memo = mpow(a,b/2); return memo*memo%MOD;}
  else return mpow(a,b-1) * a % MOD;
}
ll lpow(ll a, ll b){
  if(b==0) return 1;
  else if(b%2==0){ll memo = lpow(a,b/2); return memo*memo;}
  else return lpow(a,b-1) * a;
}
ll gcd(ll a, ll b){
  if(b==0) return a;
  else return gcd(b, a%b);
}
vector<ll> kaijo_memo;
ll kaijo(ll n){
  if(kaijo_memo.size() > n) return kaijo_memo[n];
  if(kaijo_memo.size() == 0) kaijo_memo.push_back(1);
  while(kaijo_memo.size() <= n) kaijo_memo.push_back(kaijo_memo[kaijo_memo.size()-1] * kaijo_memo.size() % MOD);
  return kaijo_memo[n];
}
vector<ll> gyaku_kaijo_memo;
ll gyaku_kaijo(ll n){
  if(gyaku_kaijo_memo.size() > n) return gyaku_kaijo_memo[n];
  if(gyaku_kaijo_memo.size() == 0) gyaku_kaijo_memo.push_back(1);
  while(gyaku_kaijo_memo.size() <= n) gyaku_kaijo_memo.push_back(gyaku_kaijo_memo[gyaku_kaijo_memo.size()-1] * mpow(gyaku_kaijo_memo.size(), MOD-2) % MOD);
  return gyaku_kaijo_memo[n];
}

ll nCr(ll n, ll r){
  if(n == r) return 1;//0個の丸と-1個の棒みたいな時に時に効く？不安.
  if(n < r || r < 0) return 0;
  ll ret = 1;
  if(n <= 1e7){
    ret *= kaijo(n); ret %= MOD;
    ret *= gyaku_kaijo(r); ret %= MOD;
    ret *= gyaku_kaijo(n-r); ret %= MOD;
  }else{
    rep(i,r){
      ret *= n-i; ret %= MOD;
      ret *= mpow(r-i, MOD-2); ret %= MOD;
    }
  }
  return ret;
}

struct hoge{
  ll y,x,t;
  pair<ll,ll> d;
};

int main(void){
  fast_io
  cout<<fixed<<setprecision(15);

  ll h,w,k;cin>>h>>w>>k;
  ll x1,y1,x2,y2;cin>>y1>>x1>>y2>>x2;x1--;y1--;x2--;y2--;
  vector<string> S(h);
  rep(y,h){
    cin>>S[y];
  }
  //dp[y][x][j]: (y,x)に行く方法のうち最後の移動がUDLR[j]であるもののうち、最小手数, 最小歩数
  vector<vector<vector<pair<ll,ll>>>> dp(h);
  rep(y,h){
    dp[y] = vector<vector<pair<ll,ll>>>(w);
    rep(x,w){
      dp[y][x] = vector<pair<ll,ll>>(4, {LINF,LINF});
    }
  }

  auto cmp = [](const hoge& l, const hoge& r){
    return l.d > r.d;
  };
  priority_queue<hoge, vector<hoge>, decltype(cmp)> q(cmp);
  rep(t,4){
    q.push({y1,x1,t,{0,0}});
  }

  
  while(q.size() > 0){
    hoge fuga = q.top();
    q.pop();
    ll y = fuga.y;
    ll x = fuga.x;
    if(y < 0 || y >= h || x < 0 || x >= w) continue;
    if(S[y][x] == '@') continue;
    ll t = fuga.t;
    auto d = fuga.d;
    if(dp[y][x][t] < d) continue;
    dp[y][x][t] = d;
    rep(ti,4){
      auto c = d;
      if(ti == t){
        c.second++;
        if(c.second == k+1){
          c.first++;
          c.second = 1;
        }
      }else{
        c.first++;
        c.second = 1;
      }

      ll ny = y, nx = x;
      if(ti == 0){
        ny = y-1;
      }else if(ti == 1){
        ny = y+1;
      }else if(ti == 2){
        nx = x-1;
      }else{
        nx = x+1;
      }

      if(ny < 0 || ny >= h || nx < 0 || nx >= w) continue;

      if(dp[ny][nx][ti] <= c) continue;
      dp[ny][nx][ti] = c;
      q.push({ny,nx,ti,c});
    }
  }

  pair<ll,ll> ans = {LINF,LINF};
  rep(t,4){
    pair<ll,ll> fuga = dp[y2][x2][t];
    if(fuga.first == LINF) continue;
    if(fuga.second > 0){
      fuga.first++;
      fuga.second = 0;
    }
    chmin(ans,fuga);
  }
  if(ans.first == LINF){
    cout<<-1<<endl;
    return 0;
  }
  cout<<ans.first<<endl;
  return 0;
}

Measured memory_bytes: 126780