#include<bits/stdc++.h>
#define F first
#define S second
#define X first
#define Y second
#define MAX 6000005
#define oo 1e18
#define mod 1000000007
#define fast_in ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);cout.setf(ios::fixed);cout.precision(0);
using namespace std;
typedef long long ll;
#define pll pair<ll , ll>
#define vll vector<ll>
#define vvll vector<vll>
#define vpll vector<pll>
#define ppp pair<pair<pll,pll>,pll>
pll d[4]={{0,1},{0,-1},{1,0},{-1,0}},s,e;
string a[MAX],asd;ll m,k,n;
ppp inv(ppp h){
h.F.F.F*=-1;h.F.F.S*=-1;
h.F.S.F*=-1;h.F.S.S*=-1;
return h;
}
int main(){
fast_in
cin>>n>>m>>k>>s.X>>s.Y>>e.X>>e.Y;
ll pass[n+5][m+5];
for(int i=0;i<=m+1;i++){
a[0]+='*';a[n+1]='*';
}
for(int i=1;i<=n;i++){
cin>>asd;
a[i]+='*';a[i]+=asd;a[i]+='*';
for(int j=0;j<=m+1;j++)pass[i][j]=-1;
}
priority_queue<ppp> q;
q.push(inv({{{0,k},{k,k}},s}));
while(!q.empty()){
ppp u=inv(q.top());q.pop();
if(pass[u.S.X][u.S.Y]!=-1)continue;
if(u.S.X==e.X && u.S.Y==e.Y){cout<<u.F.F.F;return 0;}
// cout<<u.S.X<<" "<<u.S.Y<<" "<<u.F.F.F<<" "<<u.F.F.S<<" "<<u.F.S.F<<" "<<u.F.S.S<<"\n";
pass[u.S.X][u.S.Y]=u.F.F.F;
for(int i=0;i<4;i++){
pll w1={u.S.X+d[i].F,u.S.Y+d[i].S};
if(a[w1.X][w1.Y]=='*')continue;
ppp w={u.F,w1};
if(w.F.F.S==k){
if(a[w1.X][w1.Y]=='.'){
q.push(inv(w));continue;
}
// cout<<w1.X<<" "<<w1.Y<<"\n";
w.F={{w.F.F.F+1,0},{0,0}};
}
w.F.S.F+=abs(d[i].F);
w.F.S.S+=abs(d[i].S);
w.F.F.S=max(w.F.S.F,w.F.S.S);
q.push(inv(w));
}
}
return 0;
}
