//Sylwia Sapkowska
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;
void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << "'" << x << "'";}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7, K = 30;
const int mod = 998244353;
void solve(){
int n, m, k; cin >> n >> m >> k;
T s, e; cin >> s.first >> s.second;
cin >> e.first >> e.second;
vector a(n+1, vector<char>(m+1));
for (int i = 1; i<=n; i++){
for (int j = 1; j<=m; j++){
cin >> a[i][j];
}
}
auto in = [&](T ss){
return ss.first >= 1 && ss.second >= 1 && ss.first <= n && ss.second <= m;
};
queue<T>q, q2;
vector<set<int>>tab(n+1);
for (int i = 1; i<=n; i++){
for (int j = 1; j<=m; j++){
tab[i].insert(j);
}
}
vector<int>X = {-1, 1, 0, 0};
vector<int>Y = {0, 0, -1, 1};
vector dist(n+1, vector<int>(m+1, oo));
dist[s.first][s.second] = 0;
q.push(s);
tab[s.first].erase(s.second);
while (dist[e.first][e.second] == oo){
while ((int)q.size()){
auto v = q.front(); q.pop();
for (int ck = 0; ck < 4; ck++){
T x = {v.first + X[ck], v.second + Y[ck]};
if (!in(x)) continue;
if (a[x.first][x.second] == '.'){
if (dist[x.first][x.second] == oo){
dist[x.first][x.second] = dist[v.first][v.second];
tab[x.first].erase(x.second);
q.push(x);
}
}
}
q2.push(v);
}
auto v = q2.front(); q2.pop();
debug(v);
//?opt - set aktywnych wierszy?
for (int i = max(1ll, v.first - k); i<=min(n, v.first+k); i++){
int from = (i == v.first - k || i == v.first + k ? max(1ll, v.second-k+1) : max(1ll, v.second-k));
int to = (i == v.first - k || i == v.first + k ? min(m, v.second+k-1) : min(m, v.second+k));
for (auto now = tab[i].lower_bound(from); now != tab[i].end() && *now <= to; now++){
dist[i][*now] = dist[v.first][v.second]+1;
q.push({i, *now});
}
while (1){
auto it2 = tab[i].lower_bound(from);
if (it2 == tab[i].end() || *it2 > to) break;
tab[i].erase(it2);
}
}
}
// for (int i = 1; i<=n; i++){
// for (int j = 1; j<=m; j++){
// cerr << dist[i][j] << " ";
// }
// cerr << "\n";
// }
cout << dist[e.first][e.second] << "\n";
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}
