#include <bits/stdc++.h>
 
//    #include <boost/multiprecision/cpp_int.hpp>
// #define int long long
 #define inf  1000000007
 #define pa pair<int,int>
 #define ll long long
 #define pal pair<double,double>
 #define ppap pair<pa,int>
  #define PI 3.14159265358979323846
  #define paa pair<int,char>
  #define  mp make_pair
  #define  pb push_back
  #define EPS (1e-8)
                                          
    int dx[8]={0,1,0,-1,1,1,-1,-1};
    int dy[8]={1,0,-1,0,-1,1,1,-1};
                                            using namespace std;
                                   			class pa3{
                                            	public:
                                            	int x;
                                   				int y,z;
                                            	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
                                            	bool operator < (const pa3 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		 return z<p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                   				bool operator > (const pa3 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		 return z>p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa3 &p) const{
                                            		return x==p.x && y==p.y && z==p.z;
                                            	}
                                            		bool operator != (const pa3 &p) const{
                                            			return !( x==p.x && y==p.y && z==p.z);
                                            	}
                                            
                                            };
                                            
                                            class pa4{
                                            	public:
                                            	int x;
                                            	int y,z,w;
                                            	pa4(int x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
                                            	bool operator < (const pa4 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		if(z!=p.z)return z<p.z;
                                            		return w<p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator > (const pa4 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		if(z!=p.z)return z>p.z;
                                            		return w>p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa4 &p) const{
                                            		return x==p.x && y==p.y && z==p.z &&w==p.w;
                                            	}
                                            		
                                            
                                            };
                                            class pa2{
                                            	public:
                                            	int x,y;
                                            	pa2(int x=0,int y=0):x(x),y(y) {}
                                            	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
                                            	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
                                            	bool operator < (const pa2 &p) const{
                                            		return y != p.y ? y<p.y: x<p.x;
                                            	}
                                            	bool operator > (const pa2 &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa2 &p) const{
                                            		return abs(x-p.x)==0 && abs(y-p.y)==0;
                                            	}
                                            	bool operator != (const pa2 &p) const{
                                            		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
                                            	}
                                            		
                                            
                                            };
                                            
 
                      
                                string itos( int i ) {
                                ostringstream s ;
                                s << i ;
                                return s.str() ;
                                }
                                 
                                int gcd(int v,int b){
                                	if(v==0) return b;
                                	if(b==0) return v;
                                	if(v>b) return gcd(b,v);
                                	if(v==b) return b;
                                	if(b%v==0) return v;
                                	return gcd(v,b%v);
                                }
                 
                            
                                int mod;
int extgcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    int d = extgcd(b, a%b, y, x);
    y -= a/b * x;
    return d;
}
pa operator+(const pa & l,const pa & r) {   
    return {l.first+r.first,l.second+r.second};                                    
}    
pa operator-(const pa & l,const pa & r) {   
    return {l.first-r.first,l.second-r.second};                                    
}  
                int beki(int wa,int rr,int warukazu){
                	if(rr==0) return 1%warukazu;
                	if(rr==1) return wa%warukazu;
                	wa%=warukazu;
                	if(rr%2==1) return ((ll)beki(wa,rr-1,warukazu)*(ll)wa)%warukazu;
                	ll zx=beki(wa,rr/2,warukazu);
                	return (zx*zx)%warukazu;
                }
 
                              
                int pr[1000100];
                int inv[1000010];
                

                
    			int comb(int nn,int rr){
    				if(rr<0 || rr>nn || nn<0) return 0;
    				int r=pr[nn]*inv[rr];
    				r%=mod;
    				r*=inv[nn-rr];
    				r%=mod;
    				return r;
    			}
               
                void gya(int ert){
                	pr[0]=1;
                	for(int i=1;i<=ert;i++){
                		pr[i]=((ll)pr[i-1]*i)%mod;
                	}
                		inv[ert]=beki(pr[ert],mod-2,mod);
                	for(int i=ert-1;i>=0;i--){
                		inv[i]=(ll)inv[i+1]*(i+1)%mod;
                	}
                }
                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
 //   mt19937(clock_per_sec);
  //  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;

string s[1000002];
set<int> sex[1000020],sey[1000020];



signed main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int h,w,k;
	cin>>h>>w>>k;
	int sx,sy,gx,gy;
	cin>>sx>>sy>>gx>>gy;
	sx--,sy--;
	gx--,gy--;
	for(int i=0;i<h;i++){
		cin>>s[i];

	}
	vector<vector<int>> X1(h,vector<int>(w));
	for(int i=0;i<h;i++)for(int j=0;j<w;j++){
		if(s[i][j]=='@')X1[i][j]=j;
		else if(j==0)X1[i][j]=-1;
		else X1[i][j]=X1[i][j-1];
	}
	
	vector<vector<int>> X2(h,vector<int>(w));
	for(int i=0;i<h;i++)for(int j=w-1;j>=0;j--){
		if(s[i][j]=='@')X2[i][j]=j;
		else if(j==w-1)X2[i][j]=w;
		else X2[i][j]=X2[i][j+1];
	}
	
	vector<vector<int>> Y1(h,vector<int>(w));
	for(int i=0;i<h;i++)for(int j=0;j<w;j++){
		if(s[i][j]=='@')Y1[i][j]=i;
		else if(i==0)Y1[i][j]=-1;
		else Y1[i][j]=Y1[i-1][j];
	}
	
	vector<vector<int>> Y2(h,vector<int>(w));
	for(int i=h-1;i>=0;i--)for(int j=0;j<w;j++){
		if(s[i][j]=='@')Y2[i][j]=i;
		else if(i==h-1)Y2[i][j]=h;
		else Y2[i][j]=Y2[i+1][j];
	}
	
	
	
	
	
	queue<pa3> qu;
	for(int i=0;i<h;i++)for(int j=0;j<w;j++){
		sex[i].insert(j);
		sey[j].insert(i);
	}
//	cout<<"d"<<endl;
		qu.push((pa3){sx,sy,0});
	while(qu.size()){
		pa3 z=qu.front();
		qu.pop();
		if(z.x==gx && z.y==gy){
			cout<<z.z<<endl;
			return 0;
		}
		int x=z.x,y=z.y;
	//	cout<<x<<" "<<y<<" "<<z.z<<endl;
		int si=max(y-k,X1[x][y]+1);
		int ue=min(y+k,X2[x][y]-1);
//		cout<<X2[x][y]<<endl;
//		cout<<si<<" "<<ue<<endl;
		while(1){
			
			auto it=sex[x].lower_bound(si);
			if(it==sex[x].end()||*it>ue)break;
			sey[*it].erase(x);
			qu.push((pa3){x,*it,z.z+1});
			sex[x].erase(it);
		}
		
		 si=max(x-k,Y1[x][y]+1);
		 ue=min(x+k,Y2[x][y]-1);
	//	cout<<si<<" "<<ue<<endl;
		while(1){
			auto it=sey[y].lower_bound(si);
		//	cout<<(*it)<<endl;
			if(it==sey[y].end()||*it>ue)break;
			sex[*it].erase(y);
			qu.push((pa3){*it,y,z.z+1});
			sey[y].erase(it);
		}
		
	//cout<<"d"<<endl;
	}
	cout<<-1<<endl;
	return 0;
 }


Measured memory_bytes: 239260