// no pragma

#include <bits/stdc++.h>

using namespace std;

#define pii pair<int,int>
#define fi first
#define se second
#define mp make_pair

const int inf = 1e9;

int n, m, k, xs, ys, xf, yf;

vector<vector<int>> f;
vector<vector<char>> t;
vector<vector<vector<bool>>> vis;

int dx[4] = {0,0,-1,1}, dy[4] = {-1,1,0,0};

bool valid(int x,int y){
	return (x>0 && y>0 && x<=n && y<=m && t[x][y]!='@');
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> n >> m >> k >> xs >> ys >> xf >> yf;
	f.assign(n+1,vector<int>(m+1,inf));
	vis.assign(n+1,vector<vector<bool>>(m+1,vector<bool>(4)));
	t.assign(n+1,vector<char>(m+1));
	
	for(int i=1;i<=n;++i){
		for(int j=1;j<=m;++j){
			cin >> t[i][j];
		}
	}
	
	// Dijkstra
	queue<pii> q;
	q.push({xs,ys});
	f[xs][ys] = 0;
	while(!q.empty()){
		auto now = q.front();
		q.pop();
		int x,y;
		tie(x,y) = now;
			// 4 directions
			for(int i=0;i<4;++i){
				for(int j=1;j<=k;++j){
					int nx = x+j*dx[i],ny = y+j*dy[i];
					if(!valid(nx,ny) || f[nx][ny]<=f[x][y]) break;
					else if(f[nx][ny]==inf) f[nx][ny] = f[x][y]+1, q.push({nx,ny});
				}
			}
	}	
	cout << (f[xf][yf]==inf ? -1 : f[xf][yf]);
}