//#include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;


#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)

 
typedef long double dd;
#define i_7 (ll)(1E9+7)
//#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define rrep(i,r,l) for(ll i=r;i>=l;i--)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-9;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define endl "\n"
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=1000;
    rep(y,1,P){
        ll x=mod(y*k);
        if(x+P>=i_7){
            x-=i_7;
        }
        if(abs(x)<=P){
            cout<<x<<"/"<<y<<endl;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
//////////////////////////


ll h,w,K;
bool valid(ll i,ll j){
    if(0<=i&&i<=h-1&&0<=j&&j<=w-1)return true;
    return false;
}
int main(){fastio
    cin>>h>>w>>K;
    ll x1,y1,x2,y2;cin>>x1>>y1>>x2>>y2;
    x1--;x2--;y1--;y2--;
    string s[h];rep(i,0,h-1)cin>>s[i];
    ll dp[h][w];rep(i,0,h-1)rep(j,0,w-1)dp[i][j]=inf;
    dp[x1][y1]=0;
    queue<l_l>q;
    q.push({x1,y1});
    ll kan[h][w][4];memset(kan,0,sizeof(kan));
    rep(i,0,h-1){
        rep(j,0,w-1){
            if(s[i][j]!='.'){
                kan[i][j][0]=0;continue;
            }
            if(i==0){
                kan[i][j][0]=0;
            }else{
                kan[i][j][0]=kan[i-1][j][0]+1;
            }
        }
    }
    rrep(i,h-1,0){
        rep(j,0,w-1){
            if(s[i][j]!='.'){
                kan[i][j][1]=0;continue;
            }
            if(i==h-1){
                kan[i][j][1]=0;
            }else{
                kan[i][j][1]=kan[i+1][j][1]+1;
            }
        }
    }
    rep(i,0,h-1){
        rep(j,0,w-1){
            if(s[i][j]!='.'){
                kan[i][j][2]=0;continue;
            }
            if(j==0){
                kan[i][j][2]=0;
            }else{
                kan[i][j][2]=kan[i][j-1][2]+1;
            }
        }
    }
    rep(i,0,h-1){
        rrep(j,w-1,0){
            if(s[i][j]!='.'){
                kan[i][j][3]=0;continue;
            }
            if(j==w-1){
                kan[i][j][3]=0;
            }else{
                kan[i][j][3]=kan[i][j+1][3]+1;
            }
        }
    }
    //rep(z,0,3){rep(i,0,h-1){rep(j,0,w-1)cout<<kan[i][j][z]<<" ";cout<<endl;}cout<<endl;}
    
    while(!q.empty()){
        l_l f=q.front();q.pop();
        
        
        rep(i,1,K){
            if(kan[f.fi][f.se][1]<i)break;
            ll nx=f.fi+i;
            ll ny=f.se;
            if(valid(nx,ny)&&s[nx][ny]=='.'){
                if(chmin(dp[nx][ny],dp[f.fi][f.se]+1)){
                    q.push({nx,ny});
                }else if(dp[nx][ny]<dp[f.fi][f.se]+1){
                    break;
                }
            }else{
                break;
            }
        }
        rep(i,1,K){
            if(kan[f.fi][f.se][0]<i)break;
            ll nx=f.fi-i;
            ll ny=f.se;
            if(valid(nx,ny)&&s[nx][ny]=='.'){
                if(chmin(dp[nx][ny],dp[f.fi][f.se]+1)){
                    q.push({nx,ny});
                }else if(dp[nx][ny]<dp[f.fi][f.se]+1){
                    break;
                }
            }else{
                break;
            }
        }
        rep(i,1,K){
            if(kan[f.fi][f.se][3]<i)break;
            ll nx=f.fi;
            ll ny=f.se+i;
            if(valid(nx,ny)&&s[nx][ny]=='.'){
                if(chmin(dp[nx][ny],dp[f.fi][f.se]+1)){
                    q.push({nx,ny});
                }else if(dp[nx][ny]<dp[f.fi][f.se]+1){
                    break;
                }
            }else{
                break;
            }
        }
        rep(i,1,K){
            if(kan[f.fi][f.se][2]<i)break;
            ll nx=f.fi;
            ll ny=f.se-i;
            if(valid(nx,ny)&&s[nx][ny]=='.'){
                if(chmin(dp[nx][ny],dp[f.fi][f.se]+1)){
                    q.push({nx,ny});
                }else if(dp[nx][ny]<dp[f.fi][f.se]+1){
                    break;
                }
            }else{
                break;
            }
        }
    }
    if(dp[x2][y2]>=inf/2)dp[x2][y2]=-1;
    cout<<dp[x2][y2]<<endl;
    
    return 0;
}


Measured memory_bytes: 45344