#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<int>> d;
void solve(){
cin >> N >> M >> L;
cin >> sx >> sy >> tx >> ty;
a.resize(N + 3, vector<char>(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;
q.push({sx, sy});
d[sx][sy] = 0;
while(true){
vector<pair<int, int>> pos;
while(sz(q)){
int x = q.front().fi;
int y = q.front().se;
q.pop();
pos.push_back({x, y});
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] == '#') continue;
if(minimize(d[nx][ny], d[x][y])){
q.push({nx, ny});
}
}
}
for(auto o: pos){
queue<pair<int, int>> qq;
qq.push({o.fi, o.se});
if(o.fi > L && minimize(d[o.fi - L][o.se], d[o.fi][o.se] + 1)) qq.push({o.fi - L, o.se}), q.push({o.fi - L, o.se});
if(o.se > L && minimize(d[o.fi][o.se - L], d[o.fi][o.se] + 1)) qq.push({o.fi, o.se - L}), q.push({o.fi, o.se - L});
if(o.fi + L <= N && minimize(d[o.fi + L][o.se], d[o.fi][o.se] + 1)) qq.push({o.fi + L, o.se}), q.push({o.fi + L, o.se});
if(o.se + L <= M && minimize(d[o.fi][o.se + L], d[o.fi][o.se] + 1)) qq.push({o.fi, o.se + L}), q.push({o.fi, o.se + L});
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 < 1 || nx > N || ny < 1 || ny > M) continue;
int t1 = abs(nx - o.fi), t2 = abs(ny - o.se);
if(t1 > L || t2 > L || t1 + t2 == 2 * L) continue;
if(d[o.fi - 1][o.se] == d[o.fi][o.se] && nx < o.fi) continue;
if(d[o.fi + 1][o.se] == d[o.fi][o.se] && nx > o.fi) continue;
if(d[o.fi][o.se - 1] == d[o.fi][o.se] && ny < o.se) continue;
if(d[o.fi][o.se + 1] == d[o.fi][o.se] && ny > o.se) continue;
if(minimize(d[nx][ny], d[o.fi][o.se] + 1)){
qq.push({nx, ny});
q.push({nx, ny});
}
}
}
}
if(d[tx][ty] < INF) 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;
}
