#include<bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
#define fi first
#define se second
typedef long long ll;
typedef pair<ll,ll> pll;
typedef long double ld;
const ll inf=1e9+7;
const ll mod=998244353;
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
signed main(){
    ll h,w,k;cin>>h>>w>>k;
    vector<vector<ll> >d(h+2,vector<ll>(w+2));
    vector<vector<ll> >ans(h+2,vector<ll>(w+2,inf));
    queue<pll>q;
    ll x,y;cin>>x>>y;
    q.push(mp(x,y));
    ans[x][y]=0;
    cin>>x>>y;
    rep(i,h){
        rep(j,w){
            char c;cin>>c;
            if(c=='.')d[i+1][j+1]=1;
        }
    }
    while(!q.empty()){
        pll p=q.front();
        ll nx=p.fi,ny=p.se;
        q.pop();
        rep(i,4){
            REP(j,1,k+1){
                ll xx=nx+dx[i]*j,yy=ny+dy[i]*j;
                if(d[xx][yy]==0)break;
                if(ans[xx][yy]<ans[nx][ny]+1)break;
                if(ans[xx][yy]==ans[nx][ny]+1)continue;
                if(ans[xx][yy]==inf){
                    ans[xx][yy]=ans[nx][ny]+1;
                    q.push(mp(xx,yy));
                }
            }
        }
    }
    if(ans[x][y]<inf){
        cout<<ans[x][y]<<endl;
    }else{
        cout<<-1<<endl;
    }
}
