#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T>& V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> >& Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T>& mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }
template<typename T>vector<T> make_v(size_t a){return vector<T>(a);}
template<typename T,typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}
template<typename T,typename V> typename enable_if<is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename enable_if<is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
/*
 <url:https://atcoder.jp/contests/abc170/tasks/abc170_f>
 問題文============================================================
 F - Pond Skater
 =================================================================
 解説=============================================================
 ================================================================
 */

template<class Type>
Type solve(Type res = Type()){
    int H,W,K; cin >> H >> W >> K;
    pii s,g; cin >> s.first >> s.second >> g.first >> g.second;
    s.first--; s.second--; g.first--; g.second--;
    auto c = make_v<char>(H,W);
    for(auto& vec:c) for(auto& in:vec) cin >> in;
    
    int dir[4] = {1,0,-1,0};
    auto dist = make_v<int>(H,W);
    fill_v(dist,INF);
    
    set<pii> st[2];
    int cur = 0,next = 1;
    st[cur].emplace(s);
    dist[s.first][s.second] = 0;
    while(st[cur].size()){
        for(auto& p:st[cur]){
            int x,y; tie(x,y) = p;
            for(int k = 0; k < 4;k++){
                for(int cnt = 1; cnt <= K; cnt++){
                    int nx = x + dir[k]*cnt;
                    int ny = y + dir[k^1]*cnt;
                    if(nx < 0 || nx >= H || ny < 0 || ny >= W) break;
                    if(c[nx][ny] == '@') break;
                    // if(dist[nx][ny] != INF) break;
                    if(dist[nx][ny] <= dist[x][y]) break;
                    dist[nx][ny] = dist[x][y] + 1;
                    st[next].emplace(nx,ny);
                }
            }
        }
        swap(cur,next);
        st[next].clear();
    }
    // cout << dist << endl;
    res = dist[g.first][g.second];
    
    if(res == INF) res = -1;
    return res;
}
int main(void) {
    cin.tie(0); ios_base::sync_with_stdio(false);
    // solve(0);
    cout << fixed << setprecision(15) << solve<ll>() << endl;
    return 0;
}


Measured memory_bytes: 13592