#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}


template<typename Monoid>
struct SegmentTree{
    using F=function<Monoid(Monoid,Monoid)>;
    int sz;
    vector<Monoid> seg;
    const F f;
    const Monoid gen;
    SegmentTree(int n,const F f,const Monoid &gen):f(f),gen(gen){
        sz=1;
        while(sz<n)sz<<=1;
        seg.assign(2*sz,gen);
    }
    void set(int k,const Monoid &x){
        seg[k+sz]=x;
    }
    void build(){
        for(int k=sz-1;k>0;k--) seg[k]=f(seg[2*k],seg[2*k+1]);
    }
    void update(int k,const Monoid &x){
        k+=sz;
        seg[k]=x;
        while(k>>=1) seg[k]=f(seg[2*k],seg[2*k+1]);
    }
   // [a,b)
    Monoid query(int a,int b){
        Monoid L=gen,R=gen;
        for(a+=sz,b+=sz;a<b;a>>=1,b>>=1){
            if(a&1) L=f(L,seg[a++]);
            if(b&1) R=f(seg[--b],R);
        }
        return f(L,R);
    }
    Monoid operator[](const int &k)const {
       return seg[k+sz];
    }
};
int f(int a,int b){
    return a<b?a:b;
}


signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int h,w,k;cin>>h>>w>>k;
    int sh,sw,gh,gw;cin>>sh>>sw>>gh>>gw;
    sh--,sw--,gh--,gw--;
    string s[h];
    rep(i,h) cin>>s[i];

    set<int> state[w],syoko[h];
    rep(i,h){
        syoko[i].insert(-1);
        syoko[i].insert(w);
    }
    rep(i,w){
        state[i].insert(-1);
        state[i].insert(h);
    }
    rep(i,h){
        rep(j,w){
            if(s[i][j]=='@'){
                state[j].insert(i);
                syoko[i].insert(j);
            }
        }
    }

    vector<SegmentTree<int>> segtate,segyoko;
    rep(i,w){
        SegmentTree<int> seg(h,f,INF);
        seg.build();
        segtate.push_back(seg);
    }
    rep(j,h){
        SegmentTree<int> seg(w,f,INF);
        seg.build();
        segyoko.push_back(seg);
    }

    segtate[sw].update(sh,0);
    segyoko[sh].update(sw,0);

    priority_queue<pair<int,pair<int,int>>,vector<pair<int,pair<int,int>>>,greater<pair<int,pair<int,int>>>> que;
    int ans[h][w];
    int check[h][w];
    rep(i,h)rep(j,w)ans[i][j]=INF,check[i][j]=false;
    ans[sh][sw]=0;check[sh][sw]=true;
    auto unko=[&](int ui,int uj){
        return 0<=ui and ui<h and 0<=uj and uj<w and s[ui][uj]!='@';
    };
    rep(k,4){
        int ni=sh+dx[k],nj=sw+dy[k];
        if(unko(ni,nj)){
            que.push({0,{ni,nj}});
            check[ni][nj]=true;
        }
    }
    while(!que.empty()){
        auto p=que.top();que.pop();
        int i=p.second.first,j=p.second.second;

        // cout<<i<<" "<<j<<endl;
        // rep(i,h){
        //     rep(j,w){
        //         if(ans[i][j]==INF){
        //             cout<<"I ";
        //         }else{
        //             cout<<ans[i][j]<<" ";
        //         }
        //     }
        //     cout<<endl;
        // }

        int res=INF;
        // 左右
        {
            auto ite=syoko[i].lower_bound(j);
            int l=*prev(ite)+1;
            int r=*ite-1;
            l=max(l,j-k);
            r=min(r,j+k);
            chmin(res,segyoko[i].query(l,r+1));
        }
        // 上下
        {
            auto ite=state[j].lower_bound(i);
            int d=*prev(ite)+1;
            int u=*ite-1;
            d=max(d,i-k);
            u=min(u,i+k);
            chmin(res,segtate[j].query(d,u+1));
        }
        res++;

        if(chmin(ans[i][j],res)){
            segtate[j].update(i,ans[i][j]);
            segyoko[i].update(j,ans[i][j]);
            rep(k,4){
                int ni=i+dx[k],nj=j+dy[k];
                if(unko(ni,nj)){
                    que.push({ans[i][j],{ni,nj}});
                    check[ni][nj]=true;
                }
            }
        }
    }

    if(ans[gh][gw]>=INF) cout<<-1<<endl;
    else cout<<ans[gh][gw]<<endl;
    return 0;
}


Measured memory_bytes: 273052