#include <bits/stdc++.h>
#include <experimental/random>
#include <random>
using namespace std;
using ll = long long;
using ld = long double;
const ll INF = 4e18, MOD = 1e9 + 7;
void solve();
signed main() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int q = 1;
//cin >> q;
while (q--) {
solve();
}
}
vector<pair<ll, ll>> cord = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
void solve() {
ll r, c, n;
cin >> r >> c >> n;
ll sr, sc, fr, fc;
cin >> sr >> sc >> fr >> fc;
sr--, sc--, fr--, fc--;
vector<vector<char>> a(r, vector<char>(c));
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
cin >> a[i][j];
}
}
vector<vector<ll>> dp(r, vector<ll>(c, INF));
dp[sr][sc] = 0;
deque<pair<ll, ll>> dj;
dj.emplace_back(sr, sc);
vector<vector<ll>> used(r, vector<ll>(c));
while (!empty(dj)) {
auto [x, y] = dj.front();
dj.pop_front();
for (auto [dx, dy] : cord) {
ll i = x + dx, j = y + dy;
if (i < 0 || j < 0 || i == r || j == c || a[i][j] == '#') {
continue;
}
if (dp[i][j] > dp[x][y]) {
dj.emplace_front(i, j);
dp[i][j] = dp[x][y];
}
}
for (int i = max(0ll, x - n); i < min(r, x + n + 1); i++) {
for (int j = max(0ll, y - n); j < min(c, y + n + 1); j++) {
if (abs(i - x) == n && abs(j - y) == n) {
continue;
}
if (dp[i][j] > dp[x][y] + 1) {
used[i][j]++;
dj.emplace_back(i, j);
dp[i][j] = dp[x][y] + 1;
}
}
}
}
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
if (used[i][j] > 1) {
exit(-1);
}
}
}
cout << dp[fr][fc];
}
