#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC push_options
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#include<bits/stdc++.h>
#include <xmmintrin.h>
#include <immintrin.h>
using namespace::std;
__attribute__((constructor))void init(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/priority_queue.hpp>
#include<ext/pb_ds/tag_and_trait.hpp>
// #include <boost/multiprecision/cpp_dec_float.hpp>
// #include <boost/multiprecision/cpp_int.hpp>
// namespace mp = boost::multiprecision;
// typedef mp::number<mp::cpp_dec_float<0>> cdouble;
// typedef mp::cpp_int cint;
template<typename T>using pbds=__gnu_pbds::tree<T,__gnu_pbds::null_type,less<T>,__gnu_pbds::rb_tree_tag,__gnu_pbds::tree_order_statistics_node_update>;
template<typename T>using pbds_map=__gnu_pbds::tree<T,T,less<T>,__gnu_pbds::rb_tree_tag,__gnu_pbds::tree_order_statistics_node_update>;
template<typename T,typename E>using hash_map=__gnu_pbds::gp_hash_table<T,E>;
template<typename T>using pqueue =__gnu_pbds::priority_queue<T, greater<T>,__gnu_pbds::rc_binomial_heap_tag>;
typedef long long lint;
#define INF (1LL<<60)
#define IINF (1<<30)
#define LINF (9223372036854775807LL)
#define EPS (1e-10)
#define endl ('\n')
//#define MOD 1000000007LL
#define MOD 998244353LL
//#define MOD 18446744069414584321ULL
typedef vector<lint> vec;
typedef vector<vector<lint>> mat;
typedef vector<vector<vector<lint>>> mat3;
typedef vector<string> svec;
typedef vector<vector<string>> smat;
template<typename T>inline void numout(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i<INF/2?i:"INF";f=1;}cout<<endl;}
template<typename T>inline void numout2(T t){for(auto i:t)numout(i);}
template<typename T>inline void output(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i;f=1;}cout<<endl;}
template<typename T>inline void output2(T t){for(auto i:t)output(i);}
template<typename T>inline void _output(T t){bool f=0;for(lint i=0;i<t.size();i++){cout<<f?"":" "<<t[i];f=1;}cout<<endl;}
template<typename T>inline void _output2(T t){for(lint i=0;i<t.size();i++)output(t[i]);}
#define rep(i,n) for(lint i=0;i<lint(n);++i)
#define repi(i,a,b) for(lint i=lint(a);i<(lint)(b);++i)
#define rrep(i,n) for(lint i=lint(n)-1;i>=0;--i)
#define rrepi(i,a,b) for(lint i=lint(b)-1;i>=lint(a);--i)
#define irep(i) for(lint i=0;;++i)
#define all(n) begin(n),end(n)
#define dist(a,b,c,d) sqrt(pow(a-c,2)+pow(b-d,2))
inline lint gcd(lint A,lint B){return B?gcd(B,A%B):A;}
inline lint lcm(lint A,lint B){return A/gcd(A,B)*B;}
// inline cint cgcd(cint A,cint B){return B?cgcd(B,A%B):A;}
// inline cint clcm(cint A,cint B){return A/cgcd(A,B)*B;}
bool chmin(auto& s,const auto& t){bool res=s>t;s=min(s,t);return res;}
bool chmax(auto& s,const auto& t){bool res=s<t;s=max(s,t);return res;}
const vector<lint> dx={1,0,-1,0,1,1,-1,-1};
const vector<lint> dy={0,1,0,-1,1,-1,1,-1};
#define SUM(v) accumulate(all(v),0LL)
auto call=[](auto f,auto... args){return f(f,args...);};

int main(){
    lint h,w,k;
    cin>>h>>w>>k;
    lint s,t,u,r;
    cin>>s>>t>>u>>r;
    s--;t--;u--;r--;
    vector<string>st(h);
    rep(i,h)cin>>st[i];
    priority_queue<tuple<pair<lint,lint>,lint,lint,lint>,vector<tuple<pair<lint,lint>,lint,lint,lint>>,greater<tuple<pair<lint,lint>,lint,lint,lint>>>que;
    que.emplace(make_pair(0,0),s,t,0);
    que.emplace(make_pair(0,0),s,t,1);
    vector<vector<vector<pair<lint,lint>>>>diff(h,vector<vector<pair<lint,lint>>>(w,vector<pair<lint,lint>>(2,make_pair(INF,INF))));
    diff[s][t][0]=diff[s][t][1]=make_pair(0,0);
    auto add=[&](auto s,lint dx,lint dy,lint f){
        if(f^abs(dx)){
            return make_pair(s.first+1,1LL);
        }else{
            if(s.second==k)return make_pair(s.first+1,1LL);
            else return make_pair(s.first,s.second+1);
        }
    };
    while(!que.empty()){
        auto [c,px,py,f]=que.top();
        que.pop();
        rep(t,4){
            lint x=px+dx[t];
            lint y=py+dy[t];
            if(x<0||h<=x||y<0||w<=y)continue;
            if(st[x][y]=='@')continue;
            if(chmin(diff[x][y][abs(dx[t])],add(diff[px][py][f],dx[t],dy[t],f))){
                que.emplace(diff[x][y][abs(dx[t])],x,y,abs(dx[t]));
            }
        }
    }
    if(min(diff[u][r][0].first+1,diff[u][r][1].first+1)>=INF/2){
        cout<<-1<<endl;
    }else{
        cout<<min(diff[u][r][0].first+1,diff[u][r][1].first+1)<<endl;
    }
}

Measured memory_bytes: 144988