#include <bits/stdc++.h>
using namespace std;
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, 1, -1};
int r, c, k;
bool inside(int x, int y){
return (1 <= x && x <= r && 1 <= y && y <= c);
}
void solve(){
cin >> r >> c >> k;
vector<vector<int>> d(r + 1, vector<int>(c + 1, -1));
vector<vector<int>> cell(r + 1, vector<int>(c + 1, 0));
vector<vector<int>> vis(r + 1, vector<int>(c + 1, 0));
int sx, sy, tx, ty;
cin >> sx >> sy >> tx >> ty;
for(int i = 1; i <= r; i++){
for(int j = 1; j <= c; j++){
char x; cin >> x;
if(x == '#') cell[i][j] = 1;
}
}
vector<vector<int>> rowNext(r + 1, vector<int>(c + 2));
vector<vector<int>> colNext(c + 1, vector<int>(r + 2));
for(int i = 1; i <= r; i++){
for(int j = 1; j <= c + 1; j++){
rowNext[i][j] = j;
}
}
for(int j = 1; j <= c; j++){
for(int i = 1; i <= r + 1; i++){
colNext[j][i] = i;
}
}
function<int(int, int)> findRow = [&](int row, int col) -> int {
if(col > c) return c + 1;
if(rowNext[row][col] == col) return col;
return rowNext[row][col] = findRow(row, rowNext[row][col]);
};
function<int(int, int)> findCol = [&](int col, int row) -> int {
if(row > r) return r + 1;
if(colNext[col][row] == row) return row;
return colNext[col][row] = findCol(col, colNext[col][row]);
};
auto del = [&](int x, int y){
rowNext[x][y] = findRow(x, y + 1);
colNext[y][x] = findCol(y, x + 1);
};
deque<pair<int, int>> q;
q.push_back({sx, sy});
d[sx][sy] = 0;
del(sx, sy);
while(q.size()){
auto [x, y] = q.front();
q.pop_front();
if(vis[x][y]) continue;
vis[x][y] = 1;
for(int i = 0; i < 4; i++){
int nx = x + dx[i], ny = y + dy[i];
if(inside(nx, ny)){
if(!cell[nx][ny] && (d[nx][ny] > d[x][y] || d[nx][ny] == -1)){
d[nx][ny] = d[x][y];
q.push_front({nx, ny});
del(nx, ny);
}
}
}
for(int nny: {y - k, y + k}){
if(1 <= nny && nny <= c){
int lbound = max(1, x - (k - 1));
int rbound = min(r, x + (k - 1));
int nnx = findCol(nny, lbound);
while(nnx <= rbound){
if(d[nnx][nny] == -1){
d[nnx][nny] = d[x][y] + 1;
q.push_back({nnx, nny});
}
del(nnx, nny);
nnx = findCol(nny, nnx + 1);
}
}
}
for(int nnx: {x - k, x + k}){
if(1 <= nnx && nnx <= r){
int lbound = max(1, y - (k - 1));
int rbound = min(c, y + (k - 1));
int nny = findRow(nnx, lbound);
while(nny <= rbound){
if(d[nnx][nny] == -1){
d[nnx][nny] = d[x][y] + 1;
q.push_back({nnx, nny});
}
del(nnx, nny);
nny = findRow(nnx, nny + 1);
}
}
}
if(abs(tx - x) <= k && abs(ty - y) <= k){
if(!(abs(tx - x) == k && abs(ty - y) == k)){
if(d[tx][ty] == -1 || d[tx][ty] > d[x][y] + 1){
d[tx][ty] = d[x][y] + 1;
q.push_back({tx, ty});
}
}
}
}
cout << d[tx][ty];
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
solve();
return 0;
}
