#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update>   
using namespace std;
using namespace __gnu_pbds;
typedef long long ll; 
#define int long long
typedef unsigned long long lu;
typedef vector<ll> v;
typedef vector<vector<ll> > vv;
typedef vector<string>  vs;
typedef vector<pair<ll,ll>> vpr;
typedef long double ld;
#define f(i,n) for(ll i = 0; i < n; i++)
#define ff(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define endl "\n"
#define fi first
#define se second
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define amax(x,y) if(y>x) x=y;
#define amin(x,y) if(y<x)x=y;
#define bg(x) x.begin()
#define sz(x) (ll)x.size()
#define in(x,n) for(ll i=0;i<n;i++)cin>>x[i]
#define out(x,n) for(ll i=0;i<n;i++)cout<<x[i]<<" " 
#define mxt(a) *(max_element(a.begin(),a.end()))
#define mnt(a) *(min_element(a.begin(),a.end())
#define tc ll t;cin>>t;while(t--)
typedef pair<ll,ll> pi;
#define yes cout<<"YES\n";
#define no cout<<"NO\n";
#define yesno(f) if(f) yes else no
const v dx = {1, -1, 0, 0};
const v dy = {0, 0, 1, -1};
const ld PI = 2 * acos(0.0);
ll cel(ll x1,ll y1){if((x1%y1)==0)return x1/y1;else return x1/y1+1;}
ll power(ll a,ll b,ll m)
{
    if(b==0)
        return 1;
    ll d=power(a,b/2,m);
    d=(d*d)%m;
    if(b&1)
        d=(d*a)%m;
    return d;
}
const ll mod=1e9+7;
int MOD(int a)
{
    if(a<0)
        a+=mod;
    if(a>=mod)
        a%=mod;
    return a;
}
// set_name.find_by_order(k) It returns to an iterator to the kth element (counting from zero) in the set in O(logn) time
// set_name.order_of_key(k) It returns to the number of items that are strictly smaller than our item k in O(logn) time.
/*string operations :
str.substr (x,y) : returns a substring str[x],str[x+1],...str[x+y-1]
str.substr (x) : returns a substring str[x],... end of string

str.find(qtr) : returns the first occurenece of qtr in str */
#define valid(i,j) (i>=0 && i < h && j>=0 && j<w && grid[i][j]=='.')
int32_t main()
{
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    int h,w,k;cin>>h>>w>>k;
    int x1,y1,x2,y2;cin>>x1>>y1>>x2>>y2;
    x1--;
    x2--;
    y1--;
    y2--;
    vs grid(h);in(grid,h);
    queue<pi > que;
    que.push({x1,y1});
    const int inf=1e9;      
    vv dist(h,v(w,inf));
    dist[x1][y1]=0;
    vector<vector<bool>>vst(h,vector<bool>(w,false));
    vst[x1][y1]=true;
    while(!que.empty())
    {
         pi u=que.front();
         que.pop();
         int x=u.fi,y=u.se;
         for(int i=1;i<=k;i++)
         {
            if(!valid(x+i,y))
                break;
            if(dist[x+i][y]<=dist[x][y])
                break;
            dist[x+i][y]=1+dist[x][y];
            if(!vst[x+i][y])
            {
                que.push({x+i,y});
                vst[x+i][y]=true;
            }
         }
          for(int i=1;i<=k;i++)
         {
            if(!valid(x-i,y))
                break;
            if(dist[x-i][y]<=dist[x][y])
                break;
            dist[x-i][y]=1+dist[x][y];
            if(!vst[x-i][y])
            {
                que.push({x-i,y});
                vst[x-i][y]=true;
            }
         }
          for(int i=1;i<=k;i++)
         {
            if(!valid(x,y+i))
                break;
            if(dist[x][y+i]<=dist[x][y])
                break;
            dist[x][y+i]=1+dist[x][y];
            if(!vst[x][y+i])
            {
                que.push({x,y+i});
                vst[x][y+i]=true;
            }
         }
          for(int i=1;i<=k;i++)
         {
            if(!valid(x,y-i))
                break;
            if(dist[x][y-i]<=dist[x][y])
                break;
            dist[x][y-i]=1+dist[x][y];
            if(!vst[x][y-i])
            {
                que.push({x,y-i});
                vst[x][y-i]=true;
            }
         }
    }
    if(dist[x2][y2]>=inf)
    {
        cout<<-1<<endl;
    }
    else 
        cout<<dist[x2][y2]<<endl;

    return 0;
}

Measured memory_bytes: 19816