#include <bits/stdc++.h>
using namespace std;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(),v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL<<(n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v) { cout << #v << "=" << endl; REP(i_debug, v.size()){ cout << v[i_debug] << ","; } cout << endl; }
#define mdebug(m) { cout << #m << "=" << endl; REP(i_debug, m.size()){ REP(j_debug, m[i_debug].size()){ cout << m[i_debug][j_debug] << ","; } cout << endl;} }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for (auto &x : v) is >> x; return is; }
template<typename T> ostream &operator<<(ostream &os, vector<T> &v){ for(int i = 0; i < v.size(); i++) { cout << v[i]; if(i != v.size() - 1) cout << endl; }; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p){ cout << '(' << p.first << ',' << p.second << ')'; return os; }
template<typename T> void Out(T x) { cout << x << endl; }
template<typename T1, typename T2> void chOut(bool f, T1 y, T2 n) { if(f) Out(y); else Out(n); }

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};
//char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
//const int mod = 998244353;



signed main(){

    int H, W, K; cin >> H >> W >> K;
    int x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2;
    x1--; y1--; x2--; y2--;
    vector<string> c(H); cin >> c;

    int N = H * W;
    priority_queue<Pii, vector<Pii>, greater<Pii>> que;
    vector<mat> dp(H, mat(W, vec(4, INF)));
    dp[x1][y1][0] = 0;
    que.push(Pii(0, x1 * W + y1));

    while(!que.empty()){
        Pii p = que.top(); que.pop();
        int k = p.se / N, x = (p.se / W) % H, y = p.se % W;
        if(dp[x][y][k] != p.fi) continue;
        int x0 = x + dx[k], y0 = y + dy[k];
        if(0 <= x0 && x0 < H && 0 <= y0 && y0 < W && c[x0][y0] == '.' && dp[x0][y0][k] > p.fi + 1){
            dp[x0][y0][k] = p.fi + 1;
            que.push(Pii(dp[x0][y0][k], x0 * W + y0 + N * k));
        }

        int c = K * ((p.fi + K - 1) / K);
        REP(k0, 4){
            if(dp[x][y][k0] > c){
                dp[x][y][k0] = c;
                que.push(Pii(dp[x][y][k0], x * W + y + N * k0));
            }
        }
    }

    int ans = INF;
    REP(k, 4) chmin(ans, dp[x2][y2][k]);
    chOut(ans < INF, (ans + K - 1) / K, -1);

    return 0;
}


Measured memory_bytes: 144940