#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define miele(v) min_element(v.begin(), v.end())
#define maele(v) max_element(v.begin(), v.end())
#define SUM(v) accumulate(v.begin(), v.end(), 0LL)
#define lb(a, key) lower_bound(a.begin(),a.end(),key)
#define ub(a, key) upper_bound(a.begin(),a.end(),key)
#define COUNT(a, key) count(a.begin(), a.end(), key) 
#define BITCOUNT(x) __builtin_popcount(x)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
using P = pair <int,int>;
using WeightedGraph = vector<vector <P>>;
using UnWeightedGraph = vector<vector<int>>;
using Real = long double;
using Point = complex<Real>; //Point and Vector2d is the same!
using Vector2d = complex<Real>;
const long long INF = 1LL << 60;
const int MOD = 1000000007;
const double EPS = 1e-15;
const double PI=3.14159265358979323846;
template <typename T> 
int getIndexOfLowerBound(vector <T> &v, T x){
    return lower_bound(v.begin(),v.end(),x)-v.begin();
}
template <typename T> 
int getIndexOfUpperBound(vector <T> &v, T x){
    return upper_bound(v.begin(),v.end(),x)-v.begin();
}
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
#define DUMPOUT cerr
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
istream &operator>>(istream &is, Point &p) {
    Real a, b; is >> a >> b; p = Point(a, b); return is;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T,U> &p_var) {
    is >> p_var.first >> p_var.second;
    return is;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    DUMPOUT<<'{';
    os << pair_var.first;
    DUMPOUT<<',';
    os << " "<< pair_var.second;
    DUMPOUT<<'}';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<T> &vec) {
    DUMPOUT<<'[';
    for (int i = 0; i < vec.size(); i++) 
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
    DUMPOUT<<']';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<vector<T>> &df) {
  for (auto& vec : df) os<<vec;
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    DUMPOUT << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    DUMPOUT << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
void print() {cout << endl;}
template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
  cout << head;
  if (sizeof...(tail) != 0) cout << " ";
  print(forward<Tail>(tail)...);
}
void dump_func() {DUMPOUT << '#'<<endl;}
template <typename Head, typename... Tail>
void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(std::move(tail)...);
}
#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
int h, w;
long double k;
int f(int i, int j){
    return i*w + j;
}
P d4[4] = {{1,0},{0,1},{-1,0},{0,-1}};
signed main(void) { cin.tie(0); ios::sync_with_stdio(false);
    cin>>h>>w>>k;
    int sx, sy, gx, gy; cin>>sy>>sx>>gy>>gx;
    sx--, sy--, gx--, gy--;
    vector <vector<char>> grid(h,vector <char>(w));
    cin>>grid;
    vector<vector<vector<long double>>> d (h, vector<vector<long double>>(w, vector<long double>(4, 2000001)));
    d[sy][sx][0] = d[sy][sx][1] = d[sy][sx][2] = d[sy][sx][3] = 0;
    
    priority_queue <tuple <long double, int,int,int>, vector <tuple <long double, int,int,int>>, greater <tuple <long double, int,int,int>>> pq;
    pq.push({0, sy, sx, 0}), pq.push({0, sy, sx, 1}), pq.push({0, sy, sx, 2}), pq.push({0, sy, sx, 3});
    while(!pq.empty()){
        auto tmp = pq.top(); pq.pop();
        long double cost = get <0>(tmp);
        int y = get <1>(tmp), x = get <2>(tmp), dir = get <3>(tmp);
        if(d[y][x][dir] < cost) continue;
        for(int i=0;i<4;i++){
            int ny = d4[i].F + y, nx = d4[i].S + x;
            if(ny >= 0 && ny < h && nx >= 0 && nx < w){
                if(grid[ny][nx] == '@') continue;
                if(i == dir) {if(chmin(d[ny][nx][i], cost + 1.0/k)) pq.push({d[ny][nx][i], ny, nx, i});}
                else if(chmin(d[ny][nx][i], ceil(cost)+ 1.0/k)) pq.push({d[ny][nx][i], ny, nx, i});
                //dump(ny, nx, i, d[ny][nx][i]);
            }
        }
    }
    int ans = min({ceil(d[gy][gx][0]), ceil(d[gy][gx][1]), ceil(d[gy][gx][2]), ceil(d[gy][gx][3])});
    if(ans == 2000001) print(-1); else print(ans);
}


Measured memory_bytes: 207340