#include <bits/stdc++.h>
using namespace std;
#define FOR(i,j,k) for(int i = j; i <= k; ++i)
#define pb push_back
#define pf push_front
#define pp pair<int, int>
#define F first
#define S second
#define p2 pair<pp, pp>
const int N = 2500;
int n, m, k, sx, sy, ex, ey;
int dx[8] = {0, 0, -1, 1, -1, -1, 1, 1};
int dy[8] = {-1, 1, 0, 0, -1, 1, -1, 1};
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> m >> k;
cin >> sx >> sy >> ex >> ey;
bool swp = 0;
if (n > m) swap(n, m), swp = 1;
bool a[n+1][m+1]; pp dist[n+1][m+1];
FOR(i,1,n) FOR(j,1,m) dist[i][j] = pp(-1,-1);
if (swp){
char c;
FOR(i,1,n) FOR(j,1,m){
cin >> c; a[j][i] = (c == '#');
}
swap(n, m); swap(sx, sy); swap(ex, ey);
}
else{
char c;
FOR(i,1,n) FOR(j,1,m){
cin >> c; a[i][j] = (c == '#');
}
}
deque<p2> q;
dist[sx][sy] = {0, 0};
q.pb({{sx, sy}, {0, 0}});
while (!q.empty()){
p2 t = q.front(); q.pop_front();
int x = t.F.F, y = t.F.S, d1 = t.S.F, d2 = t.S.S;
if (dist[x][y] != pp(d1, d2)) continue;
if (x == ex && y == ey){
cout << d1; return 0;
}
if (d2 < 0){
FOR(i,0,7){
int nx = x + dx[i], ny = y + dy[i];
if (nx >= 1 && nx <= n && ny >= 1 && ny <= m && (dist[nx][ny] == pp(-1, -1) || dist[nx][ny] > pp(d1, d2 + 1))){
dist[nx][ny] = pp(d1, d2 + 1);
q.pf({pp(nx, ny), pp(d1, d2 + 1)});
}
}
}
else{
FOR(i,0,3){
int nx = x + dx[i], ny = y + dy[i];
if (nx >= 1 && nx <= n && ny >= 1 && ny <= m && (dist[nx][ny] == pp(-1,-1) || dist[nx][ny] > pp(d1 + 1, 1 - k))){
dist[nx][ny] = pp(d1 + 1, 1 - k);
q.pb({pp(nx, ny), pp(d1 + 1, 1 - k)});
}
if (nx >= 1 && nx <= n && ny >= 1 && ny <= m && !a[nx][ny] && (dist[nx][ny] == pp(-1,-1) || dist[nx][ny] > pp(d1, 0))){
dist[nx][ny] = pp(d1, 0);
q.pf({pp(nx, ny), pp(d1, 0)});
}
}
}
}
cout << dist[ex][ey].F;
return 0;
}
