const int isDebugMode = 1;
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<long long, long long> P;
struct edge{long long to,cost;};
const int inf = 1 << 27;
const long long INF = 1LL << 60;
const int COMBMAX = 1001001;
const long long MOD = 1000000007;
const long long dh[] = {1, 0, -1, 0};
const long long dw[] = {0, 1, 0, -1};
string abc = "abcdefghijklmnopqrstuvwxyz";
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define eachdo(v, e) for (const auto &e : (v))
#define all(v) (v).begin(), (v).end()
#define lower_index(v, e) (long long)distance((v).begin(), lower_bound((v).begin(), (v).end(), e))
#define upper_index(v, e) (long long)distance((v).begin(), upper_bound((v).begin(), (v).end(), e))
long long mpow(long long a, long long n, long long mod = MOD){long long res = 1; while(n > 0){if(n & 1)res = res * a % mod; a = a * a % mod; n >>= 1;} return res;}
void pt(){cout << endl; return;}
template<class Head> void pt(Head&& head){cout << head; pt(); return;}
template<class Head, class... Tail> void pt(Head&& head, Tail&&... tail){cout << head << " "; pt(forward<Tail>(tail)...);}
void dpt(){if(!isDebugMode) return; cout << endl; return;}
template<class Head> void dpt(Head&& head){if(!isDebugMode) return; cout << head; pt(); return;}
template<class Head, class... Tail> void dpt(Head&& head, Tail&&... tail){if(!isDebugMode) return; cout << head << " "; pt(forward<Tail>(tail)...);}
template<class T> void debug(T v){if(!isDebugMode) return; rep(i, v.size()) cout << v[i] << " " ; cout << endl;}
template<class T> void debug2(T v){if(!isDebugMode) return; rep(i, v.size()){rep(j, v[i].size()) cout << v[i][j] << " " ; cout << endl;}}
template<class T1, class T2> inline bool chmin(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2> inline bool chmax(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2> long long gcd(T1 a, T2 b){return a % b ? gcd(b , a % b) : b;}
template<class T1, class T2> void reduce(T1 &a, T2 &b){ll g = gcd(a, b); a /= g; b /= g; return;}
bool valid(long long H, long long W, long long h, long long w) { return 0 <= h && h < H && 0 <= w && w < W; }

int main(){
    ll H, W, K; cin >> H >> W >> K;
    ll sx, sy, gx, gy; cin >> sx >> sy >> gx >> gy;
    sx--; sy--; gx--; gy--;
    vector<string> c(H);
    rep(i, H) cin >> c[i];
    vector<vector<vector<ll>>> dist(4, vector<vector<ll>>(H, vector<ll>(W, INF)));
    vector<vector<vector<bool>>> fixed(4, vector<vector<bool>>(H, vector<bool>(W, false)));
    priority_queue<pair<ll, pair<ll, P>>, vector<pair<ll, pair<ll, P>>>, greater<pair<ll, pair<ll, P>>>> que;
    que.push(make_pair(0, make_pair(0, P(sx, sy))));
    while(!que.empty()){
        pair<ll, pair<ll, P>> elem = que.top(); que.pop();
        ll cost = elem.first;
        ll dir = elem.second.first;
        ll h = elem.second.second.first;
        ll w = elem.second.second.second;
        if(fixed[dir][h][w]) continue;
        fixed[dir][h][w] = true;
        dist[dir][h][w] = cost; 
        rep(i, 4){
            if(i % 2 == dir % 2) continue;
            if(dist[i][h][w] == INF) que.push(make_pair(((cost + K - 1) / K) * K, make_pair(i, P(h, w))));
        }
        if(valid(H, W, h + dh[dir], w + dw[dir]) && c[h + dh[dir]][w + dw[dir]] == '.'){
            if(dist[dir][h + dh[dir]][w + dw[dir]] == INF) que.push(make_pair(cost + 1, make_pair(dir, P(h + dh[dir], w + dw[dir]))));
        }
    }
    pt(dist[0][gx][gy] == INF ? -1 : (dist[0][gx][gy] + K - 1) / K);
    return 0;
}

Measured memory_bytes: 60192