/**
____ ____ ____ __________________ ____ ____ ____
||I || ||c || ||e || || || ||M || ||a || ||n ||
||__|| ||__|| ||__|| ||________________|| ||__|| ||__|| ||__||
|/__\| |/__\| |/__\| |/________________\| |/__\| |/__\| |/__\|
*/
#include <iostream>
#include <chrono>
#include <vector>
#include <queue>
#define maxn 6000005
#define maxlog 20
#define INF 1000000010
#define LINF 1000000000000000005
#define endl '\n'
#define PB push_back
#define X first
#define Y second
#define control cout<<"passed"<<endl;
#pragma GCC optimize("O3" , "Ofast" , "unroll-loops" , "fast-math")
#pragma GCC target("avx2")
typedef unsigned long long ull;
typedef std::pair <int, int> pii;
typedef long long ll;
typedef std::pair <ll, ll> pll;
typedef std::pair <int, ll> pil;
typedef std::pair <ll, int> pli;
typedef long double ld;
std::chrono::high_resolution_clock::time_point startT, currT;
constexpr double TIME_MULT = 1;
double timePassed()
{
using namespace std::chrono;
currT = high_resolution_clock::now();
double time = duration_cast<duration<double>>(currT - startT).count();
return time * TIME_MULT;
}
int n, m, k;
std::string type[maxn];
pii start, endd;
pii dir[8] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}, {1, 1}, {-1, -1}, {1, -1}, {-1, 1}};
std::vector <std::vector <int> > ans, dist;
bool valid(pii node)
{
return (node.X >= 0 && node.X < n && node.Y >= 0 && node.Y < m);
}
void read()
{
std::cin >> n >> m >> k;
std::cin >> start.X >> start.Y;
std::cin >> endd.X >> endd.Y;
start.X--;
start.Y--;
endd.X--;
endd.Y--;
for(int i = 0; i < n; i++)
std::cin >> type[i];
ans.resize(n + 5);
dist.resize(n + 5);
for(int i = 0; i < n + 5; i++)
ans[i].resize(m + 5), dist[i].resize(m + 5);
for(int i = 0; i < n + 5; i++)
for(int j = 0; j < m + 5; j++)
ans[i][j] = dist[i][j] = -1;
std::vector <pii> w, b;
w.PB(start);
for(int i = 0; i < n + m + 2; i++)
{
if(i > 0)
{
std::queue <pii> q;
for(auto& e : b)
{
if(ans[e.X][e.Y] != -1)
continue;
q.push(e);
dist[e.X][e.Y] = 0;
}
b.clear();
while(q.size() != 0)
{
pii node = q.front();
q.pop();
if(ans[node.X][node.Y] != -1)
continue;
ans[node.X][node.Y] = i;
for(auto& d : dir)
{
pii nb = {node.X + d.X, node.Y + d.Y};
if(valid(nb) == false)
continue;
int dd = dist[node.X][node.Y] + 1;
if(dist[nb.X][nb.Y] != -1 && dist[nb.X][nb.Y] <= dd)
continue;
if(ans[nb.X][nb.Y] != -1)
continue;
if(dd >= k)
{
if(abs(d.X) + abs(d.Y) == 1)
{
if(type[nb.X][nb.Y] == '.')
w.PB(nb);
else
b.PB(nb);
}
continue;
}
dist[nb.X][nb.Y] = dd;
q.push(nb);
}
}
}
std::queue <pii> q;
for(auto& e : w)
{
if(ans[e.X][e.Y] != -1)
continue;
q.push(e);
}
w.clear();
while(q.size() != 0)
{
pii node = q.front();
q.pop();
if(ans[node.X][node.Y] != -1)
continue;
ans[node.X][node.Y] = i;
for(auto& d : dir)
{
if(abs(d.X) + abs(d.Y) != 1)
continue;
pii nb = {node.X + d.X , node.Y + d.Y};
if(valid(nb) == false)
continue;
if(ans[nb.X][nb.Y] != -1)
continue;
if(type[nb.X][nb.Y] == '.')
q.push(nb);
else
b.PB(nb);
}
}
}
std::cout << ans[endd.X][endd.Y] << "\n";
}
int main()
{
/**#ifdef ONLINE_JUDGE /// promeni
freopen("taxi.in", "r", stdin);
freopen("taxi.out", "w", stdout);
#endif*/
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
startT = std::chrono::high_resolution_clock::now();
read();
return 0;
}
