#include <bits/stdc++.h>
#define rep(i,a,b) for (i=a;i<b;i++)
#define rep2(i,a,b) for (i=a;i>=b;i--)
#define mod 1000000007
#define mod2 998244353
#define FIO ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define INF  1e9+5
#define f first
#define s second
#define endl '\n'
#define ll long long
#define ii pair <int,int>
#define pll pair <ll,ll>
#define vi vector <int>
#define vl vector <ll>
#define vvi vector < vi >
#define vii vector < ii >
#define vpl vector < pll >
#define vvii vector < vii >
#define vll vector < ll >
#define vb  vector <bool>
#define pb push_back
#define mk make_pair
#define eb emplace_back
#define pg priority_queue<ll, vector<ll>, greater<ll>>
#define pq priority_queue<ll>
#define sz(a) a.size()
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define cset(a) __builtin_popcountll(a)
#define FILL(a, b, T) fill_n((T *)a, sizeof(a) / sizeof(T), b)
// #define debug(x) cerr << #x << " is " << x << endl;
using namespace std;
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
#define pis pair<ll,pll>
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
    cerr << *it << " = " << a << endl;
    err(++it, args...);
}
template <typename A, typename B>
string to_string(pair<A, B> p);
 
string to_string(const string& s) {
        return '"' + s + '"';
}
 
string to_string(const char* s) {
        return to_string((string) s);
}
 
string to_string(bool b) {
        return (b ? "true" : "false");
}
 
string to_string(vector<bool> v) {
        bool first = true;
        string res = "{";
        for (int i = 0; i < static_cast<int>(v.size()); i++) {
                if (!first) {
                        res += ", ";
                }
                first = false;
                res += to_string(v[i]); 
        }
        res += "}";
        return res;
}
 
template <size_t N>
string to_string(bitset<N> v) {
        string res = "";
        for (size_t i = 0; i < N; i++) {
                res += static_cast<char>('0' + v[i]);
        }
        return res;
}
 
template <typename A>
string to_string(A v) {
        bool first = true;
        string res = "{";
        for (const auto &x : v) {
                if (!first) {
                        res += ", ";
                }
                first = false;
                res += to_string(x);
        }
        res += "}";
        return res;
}
 
template <typename A, typename B>
string to_string(pair<A, B> p) {
        return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
 
void debug_out() { 
        cerr << endl; 
}
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
        cerr << " " << to_string(H);
        debug_out(T...);
}
 
#ifndef ONLINE_JUDGE
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }
 
    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
// unordered_map<long long, int, custom_hash> safe_map;
// FOR VIEWERS, CODE STARTS HERE
ll r[4] = {-1, 1, 0, 0};
ll c[4] = {0, 0, 1, -1};
int main()
{
    FIO;
    ll t, n, m, q, maxx,  i, j, k1, k2, k3, k, x, y, flag, sum, cnt, ans, minn, cur;
    cin>>n>>m>>k1;
    ll x1, y1, x2, y2;
    cin>>x1>>y1>>x2>>y2;
    x1--;
    y1--;
    x2--;
    y2--;
    vector<string> a(n);
    vector<vector<ll>> dist(n + 1, vector<ll>(m + 1, INF));
    rep(i,0,n)
        cin>>a[i];
    queue<pll> qw;
    qw.push({x1, y1});
    dist[x1][y1] = 0;
    while( !qw.empty())
    {
        x1 = qw.front().f;
        y1 = qw.front().s;
        qw.pop();
        if( x1 == x2 and y1 == y2)
        {
            cout<<dist[x2][y2]<<endl;
            return 0;
        }
        rep(i,0,4)
        {
            rep(k,1,k1 + 1)
            {
                x = x1 + r[i]*k;
                y = y1 + c[i]*k; 
                if( x < 0 or x >= n or y < 0 or y >= m)
                    break;
                if( a[x][y] =='@' or dist[x1][y1] >= dist[x][y])
                    break;
                if( dist[x1][y1] + 1 < dist[x][y])
                {
                    qw.push({x, y});
                    dist[x][y] = dist[x1][y1] + 1;    
                }
            }
        }
    }
    cout<<"-1\n";
    return 0;
}

Measured memory_bytes: 26700