#include <bits/stdc++.h>
#define NMAX 1010
//#define int long long
#define pb push_back
#define eb emplace_back
#define MOD 1000000007
#define nl '\n'
#define INF 1000000007
#define LLONG_MAX 9223372036854775807
#define pii pair<int,int>
#define tpl tuple<int,int,int,int>
//#pragma GCC optimize("O3")
using namespace std;
ifstream fin("aib.in");
ofstream fout("aib.out");
/*
*
*
----------------DEMONSTRATION-------------------
1 2 2 3 4 2
1 2 3 4 5 6
1 2 3 4 5 6
1 2 3 4 5 6
1 2 4 5
---------------------END------------------------
*/
int r,c,n;
int i_s,j_s,i_f,j_f;
int di[]={1,-1,0,0};
int dj[]={0,0,1,-1};
bool inmat(int i,int j)
{
return i>=1 && i<=r && j>=1 && j<=c;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin>>r>>c>>n;
cin>>i_s>>j_s;
cin>>i_f>>j_f;
vector<vector<int>>mat(r+1,vector<int>(c+1));
vector<vector<int>>dist(r+1,vector<int>(c+1,-1));
queue<tpl>white,black;
for(int i=1;i<=r;++i)
{
for(int j=1;j<=c;++j)
{
char x;
cin>>x;
if(x=='.')
{
mat[i][j]=0;
}
else
{
mat[i][j]=1;
}
}
}
dist[i_s][j_s]=0;
white.push({i_s,j_s,0,0});
while(!white.empty() || !black.empty())
{
while(!black.empty())
{
auto [i,j,x,y]=black.front();
black.pop();
// cout<<i<<" "<<j<<"b"<<nl;
if(x==0 || y==0)
{
white.push({i,j,0,0});
}
for(int d=0;d<4;++d)
{
int inou=i+di[d];
int jnou=j+dj[d];
int pas_x=x-abs(di[d]);
int pas_y=y-abs(dj[d]);
if((pas_x>=0 && pas_y>=0)&& inmat(inou,jnou) && dist[inou][jnou]==-1)
{
dist[inou][jnou]=dist[i][j];
black.push({inou,jnou,pas_x,pas_y});
}
}
}
while(!white.empty())
{
auto [i,j,x,y]=white.front();
white.pop();
// cout<<i<<" "<<j<<"w"<<nl;
for(int d=0;d<4;++d)
{
int inou=i+di[d];
int jnou=j+dj[d];
if(inmat(inou,jnou) && dist[inou][jnou]==-1)
{
if(mat[inou][jnou]==1)
{
dist[inou][jnou]=dist[i][j]+1;
black.push({inou,jnou,n-1,n-1});
}
else
{
dist[inou][jnou]=dist[i][j];
white.push({inou,jnou,0,0});
}
}
}
}
}
cout<<dist[i_f][j_f];
return 0;
}
