#pragma GCC target("avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;
// #include<boost/multiprecision/cpp_int.hpp>
// namespace multiprecisioninteger = boost::multiprecision;
// using cint=multiprecisioninteger::cpp_int;
using namespace std;
using ll=long long;
#define double long double
using datas=pair<ll,ll>;
using ddatas=pair<double,double>;
using tdata=pair<ll,datas>;
using vec=vector<ll>;
using mat=vector<vec>;
using pvec=vector<datas>;
using pmat=vector<pvec>;
// using llset=tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>;
#define For(i,a,b) for(i=a;i<(ll)b;++i)
#define bFor(i,b,a) for(i=b,--i;i>=(ll)a;--i)
#define rep(i,N) For(i,0,N)
#define rep1(i,N) For(i,1,N)
#define brep(i,N) bFor(i,N,0)
#define brep1(i,N) bFor(i,N,1)
#define all(v) (v).begin(),(v).end()
#define allr(v) (v).rbegin(),(v).rend()
#define vsort(v) sort(all(v))
#define vrsort(v) sort(allr(v))
#define endl "\n"
#define eb emplace_back
#define print(v) cout<<v<<endl
#define printyes cout<<"Yes"<<endl
#define printno cout<<"No"<<endl
#define printYES cout<<"YES"<<endl
#define printNO cout<<"NO"<<endl
#define output(v) do{bool f=0;for(auto outi:v){cout<<(f?" ":"")<<outi;f=1;}cout<<endl;}while(0)
#define matoutput(v) do{for(auto outimat:v)output(outimat);}while(0)
const ll mod=1000000007;
// const ll mod=998244353;
const ll inf=1LL<<60;
const double PI = acos(-1);
const double eps = 1e-9;
template<class T> inline bool chmax(T& a,T b){bool x=a<b;if(x)a=b;return x;} 
template<class T> inline bool chmin(T& a,T b){bool x=a>b;if(x)a=b;return x;} 

void startupcpp(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<fixed<<setprecision(15);
}

double distance(ddatas x,ddatas y){
  double a=x.first-y.first,b=x.second-y.second;
  return sqrt(a*a+b*b);
}

ll modinv(ll a) {
  ll b=mod,u=1,v=0,t;
  while(b){
    t=a/b;
    a-=t*b; swap(a,b);
    u-=t*v; swap(u,v);
  }
  return (u+mod)%mod;
}

ll moddevide(ll a,ll b){return (a*modinv(b))%mod;}

vec modncrlistp,modncrlistm;

ll modncr(ll n,ll r){
  if(n<r)return 0;
  ll i,size=modncrlistp.size();
  if(size<=n){
    modncrlistp.resize(n+1);
    modncrlistm.resize(n+1);
    if(!size){
      modncrlistp[0]=modncrlistm[0]=1;
      size++;
    }
    For(i,size,n+1){
      modncrlistp[i]=modncrlistp[i-1]*i%mod;
      modncrlistm[i]=modinv(modncrlistp[i]);
    }
  }
  return modncrlistp[n]*modncrlistm[r]%mod*modncrlistm[n-r]%mod;
}

ll modpow(ll a,ll n){
  ll res=1;
  while(n>0){
    if(n&1)res=res*a%mod;
    a=a*a%mod;
    n>>=1;
  }
  return res;
}

ll gcd(ll a,ll b){if(!b)return abs(a);return (a%b==0)?abs(b):gcd(b,a%b);}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

ll countdigits(ll n){
  ll ans=0;
  while(n){n/=10;ans++;}
  return ans;
}

ll sumdigits(ll n){
  ll ans=0;
  while(n){ans+=n%10;n/=10;}
  return ans;
}

void topcoder(vector<int>& v){
  string s;
  while(1){
    cin>>s;
    int i=s[0]=='{',x=0;
    while(s[i]>='0'&&s[i]<='9'){
      x=x*10+s[i]-'0';
      ++i;
    }
    v.eb(x);
    if(s[i]=='}')break;
  }
}
void topcoder(string& s){
  string t;
  cin>>t;
  int i=1;
  while(t[i]!='"'){
    s+=t[i++];
  }
}
template <typename T>
struct BinaryIndexedTree{
  int size,bitn=0;
  T I;
  using func=function<T(T,T)>;
  func F;
  vector<T> tree;
  BinaryIndexedTree(int N,T e,func f):size(N+1),I(e),F(f),tree(size,e){}
  BinaryIndexedTree(int N):size(N+1),I(0),F([](T a,T b){return a+b;}),tree(size,0){}
  void act(int i,T x){
    for(++i;i<size;i+=-i&i){
      tree[i]=F(tree[i],x);
    }
  }
  T queli(int i){
    T res=I;
    for(++i;i>0;i-=-i&i){
      res=F(tree[i],res);
    }
    return res;
  }
  //only(N,+)
  int lower_bound(int x){
    int i=0;
    if(!bitn){
      i=size;bitn=1;
      while(i){
        i>>=1;bitn<<=1;
      }
      i=0;
    }
    for(int k=bitn;k;k>>=1){
      if(i+k<size&&tree[i+k]<x){
        i+=k;
        x-=tree[i];
      }
    }
    return i;
  }
};

int N,M,K,H,W,A,B,C,D;
vector<set<int>> h,w;
void er(int x,int y){
  h[x].erase(y);
  w[y].erase(x);
}
int main(){
  // startupcpp();
  // int codeforces;cin>>codeforces;while(codeforces--){
  int i,j;
  cin>>H>>W>>K;
  if(H<=W){
    set<int> f;
    rep(i,H)f.insert(i);
    w.resize(W,f);
    For(i,H,W)f.insert(i);
    h.resize(H,f);
  }else{
    set<int> f;
    rep(i,W)f.insert(i);
    h.resize(H,f);
    For(i,W,H)f.insert(i);
    w.resize(W,f);
  }
  cin>>A>>B>>C>>D;
  --A;--B;--C;--D;
  vector<vector<bool>> ch(H,vector<bool>(W));
  vector<vector<int>> dist(H,vector<int>(W,-1));

  vector<BinaryIndexedTree<int>> hch(H,BinaryIndexedTree<int>(W+2)),wch(W,BinaryIndexedTree<int>(H+2));
  rep(i,H){
    string s;
    cin>>s;
    rep(j,W){
      if(ch[i][j]=(s[j]=='@')){
        er(i,j);
        hch[i].act(j,1);
        wch[j].act(i,1);
      }
    }
  }
  dist[A][B]=0;
  queue<int> que,erque;
  que.push(A*W+B);
  er(A,B);
  while(!que.empty()){
    int now=que.front();que.pop();
    i=now/W;
    j=now%W;

    if(h[i].size()){
    auto itr=h[i].lower_bound(j);
    if(itr!=h[i].begin()){
    --itr;
    while(*itr>=j-K&&hch[i].queli(*itr)==hch[i].queli(j)){
      erque.push(*itr);
      if(itr==h[i].begin())break;
      --itr;
    }
    }
    itr=h[i].lower_bound(j);
    while(itr!=h[i].end()&&*itr<=j+K&&hch[i].queli(*itr)==hch[i].queli(j)){
      erque.push(*itr);
      ++itr;
    }
    }
    while(!erque.empty()){
      int next=erque.front();erque.pop();
      er(i,next);
      dist[i][next]=dist[i][j]+1;
      que.push(i*W+next);
    }

    if(w[j].size()){
    auto itr=w[j].lower_bound(i);
    if(itr!=w[j].begin()){
    --itr;
    while(*itr>=i-K&&wch[j].queli(*itr)==wch[j].queli(i)){
      erque.push(*itr);
      if(itr==w[j].begin())break;
      --itr;
    }
    }
    itr=w[j].lower_bound(i);
    while(itr!=w[j].end()&&*itr<=i+K&&wch[j].queli(*itr)==wch[j].queli(i)){
      erque.push(*itr);
      ++itr;
    }
    }
    while(!erque.empty()){
      int next=erque.front();erque.pop();
      er(next,j);
      dist[next][j]=dist[i][j]+1;
      que.push(next*W+j);
    }
  }
  // matoutput(dist);
  print(dist[C][D]);
}

Measured memory_bytes: 261212