#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef long long ll;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
const int maxn = 6e6 + 10, block = sqrt(maxn) + 10;
struct cell
{
int x, y;
cell(int _x = 0, int _y = 0)
{
x = _x;
y = _y;
}
cell add(const cell &r) const
{
cell d;
d.x = x + r.x;
d.y = y + r.y;
return d;
}
};
cell neib[4] = {{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
int n, m, h;
vector < int > a[block], par[block];
vector < int > l[block], r[block];
vector < int > used[block];
int stx, sty, enx, eny;
int find_leader(int i, int j)
{
if (par[i][j] == j)
return j;
return (par[i][j] = find_leader(i, par[i][j]));
}
void unite(int x, int y, int i, int j)
{
y = find_leader(x, y);
j = find_leader(i, j);
if (y == j)
return;
l[i][j] = min(l[i][j], l[x][y]);
r[i][j] = max(r[i][j], r[x][y]);
par[x][y] = j;
}
void solve()
{
cin >> n >> m >> h;
cin >> stx >> sty;
cin >> enx >> eny;
for (int i = 1; i <= n; i ++)
{
a[i].resize(m + 2);
l[i].resize(m + 2);
r[i].resize(m + 2);
par[i].resize(m + 2);
used[i].resize(m + 2);
for (int j = 1; j <= m; j ++)
{
l[i][j] = r[i][j] = j;
par[i][j] = j;
used[i][j] = -1;
}
for (int j = 1; j <= m; j ++)
{
char c;
cin >> c;
if (c == '.')
a[i][j] = 0;
else
a[i][j] = 1;
}
}
deque < cell > q;
q.push_back(cell(stx, sty));
used[stx][sty] = 0;
while(!q.empty())
{
cell cur = q.front();
q.pop_front();
/**cout << cur.x << " : " << cur.y << " " << used[cur.x][cur.y] << endl;
for (int i = 1; i <= n; i ++, cout << endl)
for (int j = 1; j <= m; j ++)
cout << used[i][j] << " ";*/
for (int i = 0; i < 4; i ++)
{
cell nb = cur.add(neib[i]);
///cout << nb.x << " --- " << nb.y << endl;
if (nb.x > 0 && nb.x <= n && nb.y > 0 && nb.y <= m)
{
if (used[nb.x][nb.y] == -1 && a[nb.x][nb.y] == 0)
{
used[nb.x][nb.y] = used[cur.x][cur.y];
q.push_front(nb);
}
}
}
int left = max(1, cur.y - h), right = min(m, cur.y + h);
for (int i = max(1, cur.x - h); i <= min(n, cur.x + h); i ++)
{
if (i == cur.x - h || i == cur.x + h)
left ++, right --;
if (a[i][left] == 1)
{
used[i][left] = used[cur.x][cur.y] + 1;
q.push_back(cell(i, left));
a[i][left] = 0;
if (left > 1 && a[i][left - 1] == 0)
unite(i, left, i, left - 1);
if (left < m && a[i][left + 1] == 0)
unite(i, left, i, left + 1);
}
while(true)
{
///cout << "cycle " << i << " " << left << " " << right << endl;
int lead = find_leader(i, left), to = r[i][lead];
///cout << lead << " " << r[i][lead] << endl;
if (to < right)
{
if (a[i][to + 1] == 1)
{
used[i][to + 1] = used[cur.x][cur.y] + 1;
q.push_back(cell(i, to + 1));
a[i][to + 1] = 0;
}
unite(i, to, i, to + 1);
}
else
{
break;
}
}
if (i == cur.x - h || i == cur.x + h)
left --, right ++;
}
}
cout << used[enx][eny] << endl;
}
int main()
{
solve();
return 0;
}
