#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(998244353)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};
int N, M, L;
int sx, sy, tx, ty;
vector<vector<char>> a;
vector<vector<bool>> vis;
vector<vector<int>> d;
void solve(){
cin >> N >> M >> L;
cin >> sx >> sy >> tx >> ty;
a.resize(N + 3, vector<char>(M + 3, 0));
vis.resize(N + 3, vector<bool>(M + 3, 0));
d.resize(N + 3, vector<int>(M + 3, INF));
for(int i=1; i<=N; i++){
for(int j=1; j<=M; j++){
cin >> a[i][j];
}
}
queue<pair<int, int>> q[2];
q[0].push({sx, sy});
d[sx][sy] = 0;
vis[sx][sy] = true;
for(int t=0;; t++){
int i = t & 1;
vector<pair<int, int>> pos;
while(sz(q[i])){
int x = q[i].front().fi;
int y = q[i].front().se;
pos.push_back({x, y});
q[i].pop();
for(int k=0; k<4; k++){
int nx = x + dx[k], ny = y + dy[k];
if(nx < 1 || nx > N || ny < 1 || ny > M || a[nx][ny] == '#' || vis[nx][ny]) continue;
if(minimize(d[nx][ny], d[x][y])){
q[i].push({nx, ny});
vis[nx][ny] = true;
}
}
}
for(auto o: pos){
queue<pair<int, int>> qq;
qq.push({o.fi, o.se});
while(sz(qq)){
int x = qq.front().fi;
int y = qq.front().se;
qq.pop();
for(int k=0; k<4; k++){
int nx = x + dx[k], ny = y + dy[k];
if(nx < max(1, o.fi - L) || nx > min(N, o.fi + L) || ny < max(1, o.se - L)
|| ny > min(M, o.se + L) || vis[nx][ny]) continue;
if(abs(o.fi - nx) + abs(o.se - ny) >= 2 * L) continue;
if(minimize(d[nx][ny], d[o.fi][o.se] + 1)){
q[!i].push({nx, ny});
qq.push({nx, ny});
vis[nx][ny] = true;
}
}
}
}
if(vis[tx][ty]) break;
}
// for(int i=1; i<=N; i++){
// for(int j=1; j<=M; j++){
// cout << d[i][j] << ' ';
// }
// cout << '\n';
// }
cout << d[tx][ty] << '\n';
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen("flowers.inp", "r", stdin);
// freopen("flowers.out", "w", stdout);
int nTest = 1;
while(nTest--)
solve();
return 0;
}
