#include<bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define repi(n) for(int i = 0; i < (n); i++)
#define rep(i, n) for(int (i) = 0; (i) < (n); (i)++)
#define all(p) p.begin(), p.end()
#define pop_count(p) __builtin_popcountll(p)
#define len(s, e) ((e)-(s)+1)
#define mid(s, e) ((s)+((e)-(s))/2)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<int, ll> pil;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
const int MOD = 1e9 + 7;
const int oo = 987654321;
const ll OO = 1e18;
#ifdef ONLINE_JUDGE
#define endl '\n'
#endif
template <typename A, typename B>
std::istream& operator >>(std::istream& in, pair<A, B>& a) {
	in >> a.first >> a.second;
  return in;
}
template <typename T>
std::istream& operator >>(std::istream& in, vector<T>& a) {
  for (auto& v : a) in >> v;
  return in;
}
template <typename T, size_t N>
std::istream& operator >>(std::istream& in, array<T, N>& a) {
  for (int i = 0; i < N; i++) in >> a[i];
  return in;
}
template <typename A, typename B>
std::ostream& operator <<(std::ostream& out, const pair<A, B>& a) {
  out << "(" << a.first << "," << a.second << ")";
  return out;
}
template <typename T, size_t N>
std::ostream& operator <<(std::ostream& out, const array<T, N>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T, class Cmp>
std::ostream& operator <<(std::ostream& out, const set<T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
  return out;
}
template <typename U, typename T, class Cmp>
std::ostream& operator <<(std::ostream& out, const map<U, T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& p : a) { out << (first ? "" : ", "); out << p.first << ":" << p.second; first = 0;} out << "}";
  return out;
}
template <typename T>
std::ostream& operator <<(std::ostream& out, const list<T>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
#ifdef ANEEE_LOCAL
template <typename T>
std::ostream& operator <<(std::ostream& out, const vector<T>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
#else
template <typename T>
std::ostream& operator <<(std::ostream& out, const vector<T>& a) {
  for (const auto& v : a) out << v << ' ';
  return out;
}
#endif
#ifdef ANEEE_LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 7
#endif
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
	cerr <<"[" << name << ": " << arg1 << "]" << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr << "[";
  cerr.write(names, comma - names) << ": " << arg1 << "]  ";
  __f(comma + 2, args...);
}
template <typename Arg1>
void print(Arg1&& arg1){
	cout << arg1 << endl;
}
template <typename Arg1, typename... Args>
void print(Arg1&& arg1, Args&&... args){
  cout << arg1 << ' ';
  print(args...);
}
template <typename Arg1>
void read(Arg1&& arg1){
	cin >> arg1;
}
template <typename Arg1, typename... Args>
void read(Arg1&& arg1, Args&&... args){
  cin >> arg1;
  read(args...);
}

class Timer {
	string _name;
	clock_t _start;
public:
	Timer(string name = "Runtime") { _name = "["+name+": ", _start = clock(); }
	~Timer() { cerr << _name << double(clock() - _start)/CLOCKS_PER_SEC << "]\n"; }
};

#ifdef ONLINE_JUDGE
#undef CASE_INFO
#endif

struct Data {
	int x, y, dir;
	long long cost = OO;

	bool operator < (const Data o) const {
		return cost > o.cost;
	}
};

int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1};

void solve() {
	int n, m, k;
	read(n, m, k);
	int x1, y1, x2, y2;
	read(x1, y1, x2, y2);
	x1--; x2--; y1--; y2--;
	vector<string> grid(n);
	read(grid);
	priority_queue<Data> q;
	vector<vector<vector<long long>>> dis(n, vector<vector<long long>>(m, vector<long long>(4, OO)));
	for(int dir = 0; dir < 4; dir++) { q.push({x1, y1, dir, 0}); }
	while(q.size()) {
		Data cur = q.top(); q.pop();
		if(dis[cur.x][cur.y][cur.dir] < cur.cost) continue;
		for(int kk = 0; kk < 4; kk++) {
			int r = cur.x + dx[kk], c = cur.y + dy[kk];
			if(r < 0 or c < 0 or r >= n or c >= m or grid[r][c] == '@') continue;
			if(kk == cur.dir) {
				if(dis[r][c][kk] > cur.cost + 1) {
					dis[r][c][kk] = cur.cost + 1;
					q.push({r, c, kk, dis[r][c][kk]});
				}
			}
			else {
				if(dis[r][c][kk] > (cur.cost+k-1)/k*k + 1) {
					dis[r][c][kk] = (cur.cost+k-1)/k*k + 1;
					q.push({r, c, kk, dis[r][c][kk]});
				}
			}
		}
	}
	ll ans = *min_element(all(dis[x2][y2]));
	print( ans >= OO ? -1 : (ans+k-1)/k);
}

signed main() {
	Timer ti;
	std::ios_base::sync_with_stdio(false);
	cin.tie(nullptr); cout.tie(nullptr);
	int T = 1;
	#ifdef TEST_CASES
	cin >> T;
	#endif
	for(int t = 1; t <= T; t++) {
		#ifdef CASE_INFO
		cout << "Case #" << t << ": ";
		#endif
		solve();
	}
	return 0;
}


Measured memory_bytes: 145016