#include<bits/stdc++.h>

using namespace std;
#define INFS (1LL<<28)
#define DEKAI 1000000007
#define INF 1000000007
//#define MOD 1000000007
#define lp(i,n) for(int i=0;i<n;i++)
#define lps(i,n) for(int i=1;i<=n;i++)
#define all(c) begin(c), end(c)

//#define int long long

namespace {
#define __DECLARE__(C)    \
	    template <typename T> \
	std::ostream &operator<<(std::ostream &, const C<T> &);

#define __DECLAREM__(C)               \
	    template <typename T, typename U> \
	std::ostream &operator<<(std::ostream &, const C<T, U> &);

    __DECLARE__(std::vector)
    __DECLARE__(std::deque)
    __DECLARE__(std::set)
    __DECLARE__(std::stack)
    __DECLARE__(std::queue)
    __DECLARE__(std::priority_queue)
    __DECLARE__(std::unordered_set)
    __DECLAREM__(std::map)
    __DECLAREM__(std::unordered_map)

    template <typename T, typename U>
    std::ostream &operator<<(std::ostream &, const std::pair<T, U> &);
    template <typename... T>
    std::ostream &operator<<(std::ostream &, const std::tuple<T...> &);
    template <typename T, std::size_t N>
    std::ostream &operator<<(std::ostream &, const std::array<T, N> &);

    template <typename Tuple, std::size_t N>
    struct __TuplePrinter__ {
        static void print(std::ostream &os, const Tuple &t) {
            __TuplePrinter__<Tuple, N - 1>::print(os, t);
            os << ", " << std::get<N - 1>(t);
        }
    };

    template <typename Tuple>
    struct __TuplePrinter__<Tuple, 1> {
        static void print(std::ostream &os, const Tuple &t) { os << std::get<0>(t); }
    };

    template <typename... T>
    std::ostream &operator<<(std::ostream &os, const std::tuple<T...> &t) {
        os << '(';
        __TuplePrinter__<decltype(t), sizeof...(T)>::print(os, t);
        os << ')';
        return os;
    }

    template <typename T, typename U>
    std::ostream &operator<<(std::ostream &os, const std::pair<T, U> &v) {
        return os << '(' << v.first << ", " << v.second << ')';
    }

#define __INNER__                             \
	os << '[';                                \
	for (auto it = begin(c); it != end(c);) { \
		os << *it;                            \
		os << (++it != end(c) ? ", " : "");   \
	}                                         \
	return os << ']';

    template <typename T, std::size_t N>
    std::ostream &operator<<(std::ostream &os, const std::array<T, N> &c) {
        __INNER__
    }

#define __DEFINE__(C)                                           \
	    template <typename T>                                       \
	std::ostream &operator<<(std::ostream &os, const C<T> &c) { \
		__INNER__                                               \
	}

#define __DEFINEM__(C)                                             \
	    template <typename T, typename U>                              \
	std::ostream &operator<<(std::ostream &os, const C<T, U> &c) { \
		__INNER__                                                  \
	}

#define __DEFINEW__(C, M1, M2)                                  \
	    template <typename T>                                       \
	std::ostream &operator<<(std::ostream &os, const C<T> &c) { \
		std::deque<T> v;                                        \
		for (auto d = c; !d.empty(); d.pop()) v.M1(d.M2());     \
			return os << v;                                         \
	}

    __DEFINE__(std::vector)
    __DEFINE__(std::deque)
    __DEFINE__(std::set)
    __DEFINEW__(std::stack, push_front, top)
    __DEFINEW__(std::queue, push_back, front)
    __DEFINEW__(std::priority_queue, push_front, top)
    __DEFINE__(std::unordered_set)
    __DEFINEM__(std::map)
    __DEFINEM__(std::unordered_map)
}

#define pii pair<int,int>
#define ll long long
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

// modint
template <signed M, unsigned T>
struct mod_int {
    constexpr static signed MODULO = M;
    constexpr static unsigned TABLE_SIZE = T;

    signed x;

    mod_int() : x(0) {}

    mod_int(long long y) : x(static_cast<signed>(y >= 0 ? y % MODULO : MODULO - (-y) % MODULO)) {}

    mod_int(int y) : x(y >= 0 ? y % MODULO : MODULO - (-y) % MODULO) {}

    mod_int &operator+=(const mod_int &rhs) {
        if ((x += rhs.x) >= MODULO) x -= MODULO;
        return *this;
    }

    mod_int &operator-=(const mod_int &rhs) {
        if ((x += MODULO - rhs.x) >= MODULO) x -= MODULO;
        return *this;
    }

    mod_int &operator*=(const mod_int &rhs) {
        x = static_cast<signed>(1LL * x * rhs.x % MODULO);
        return *this;
    }

    mod_int &operator/=(const mod_int &rhs) {
        x = static_cast<signed>((1LL * x * rhs.inv().x) % MODULO);
        return *this;
    }

    mod_int operator-() const { return mod_int(-x); }

    mod_int operator+(const mod_int &rhs) const { return mod_int(*this) += rhs; }

    mod_int operator-(const mod_int &rhs) const { return mod_int(*this) -= rhs; }

    mod_int operator*(const mod_int &rhs) const { return mod_int(*this) *= rhs; }

    mod_int operator/(const mod_int &rhs) const { return mod_int(*this) /= rhs; }

    bool operator<(const mod_int &rhs) const { return x < rhs.x; }

    mod_int inv() const {
        assert(x != 0);
        if (x <= static_cast<signed>(TABLE_SIZE)) {
            if (_inv[1].x == 0) prepare();
            return _inv[x];
        } else {
            signed a = x, b = MODULO, u = 1, v = 0, t;
            while (b) {
                t = a / b;
                a -= t * b;
                std::swap(a, b);
                u -= t * v;
                std::swap(u, v);
            }
            return mod_int(u);
        }
    }

    mod_int pow(long long t) const {
        assert(!(x == 0 && t == 0));
        mod_int e = *this, res = mod_int(1);
        for (; t; e *= e, t >>= 1)
            if (t & 1) res *= e;
        return res;
    }

    mod_int fact() {
        if (_fact[0].x == 0) prepare();
        return _fact[x];
    }

    mod_int inv_fact() {
        if (_fact[0].x == 0) prepare();
        return _inv_fact[x];
    }

    mod_int choose(mod_int y) {
        assert(y.x <= x);
        return this->fact() * y.inv_fact() * mod_int(x - y.x).inv_fact();
    }

    static mod_int _inv[TABLE_SIZE + 1];

    static mod_int _fact[TABLE_SIZE + 1];

    static mod_int _inv_fact[TABLE_SIZE + 1];

    static void prepare() {
        _inv[1] = 1;
        for (int i = 2; i <= (int)TABLE_SIZE; ++i) {
            _inv[i] = 1LL * _inv[MODULO % i].x * (MODULO - MODULO / i) % MODULO;
        }
        _fact[0] = 1;
        for (unsigned i = 1; i <= TABLE_SIZE; ++i) {
            _fact[i] = _fact[i - 1] * int(i);
        }
        _inv_fact[TABLE_SIZE] = _fact[TABLE_SIZE].inv();
        for (int i = (int)TABLE_SIZE - 1; i >= 0; --i) {
            _inv_fact[i] = _inv_fact[i + 1] * (i + 1);
        }
    }
};

template <int M, unsigned F>
std::ostream &operator<<(std::ostream &os, const mod_int<M, F> &rhs) {
    return os << rhs.x;
}

template <int M, unsigned F>
std::istream &operator>>(std::istream &is, mod_int<M, F> &rhs) {
    long long s;
    is >> s;
    rhs = mod_int<M, F>(s);
    return is;
}

template <int M, unsigned F>
mod_int<M, F> mod_int<M, F>::_inv[TABLE_SIZE + 1];

template <int M, unsigned F>
mod_int<M, F> mod_int<M, F>::_fact[TABLE_SIZE + 1];

template <int M, unsigned F>
mod_int<M, F> mod_int<M, F>::_inv_fact[TABLE_SIZE + 1];

template <int M, unsigned F>
bool operator==(const mod_int<M, F> &lhs, const mod_int<M, F> &rhs) {
    return lhs.x == rhs.x;
}

template <int M, unsigned F>
bool operator!=(const mod_int<M, F> &lhs, const mod_int<M, F> &rhs) {
    return !(lhs == rhs);
}

const int MF = 1000010;
const int MOD = 1000000007;

using mint = mod_int<MOD, MF>;

mint binom(int n, int r) { return (r < 0 || r > n || n < 0) ? 0 : mint(n).choose(r); }

mint fact(int n) { return mint(n).fact(); }

mint inv_fact(int n) { return mint(n).inv_fact(); }
const ll mod = 1000000007;
const int MAX_N = 10000;  // 400MB
// const int MAX_N = 1024; // 4MB
// nCr % mod

#define int long long

inline ll gcds(ll a, ll b) { return b ? gcds(b, a % b) : a; }
inline ll lcms(ll a, ll b) { return a / gcd(a, b) * b; }

#define RK 200000000000
#define LK 300000000000
#define PL 400000000000
#define MI 500000000000
#define KA 600000000000
#define PI acos(-1)
//#define double float

signed main(){
	int h,w,k;
	cin>>h>>w>>k;
	int sx,sy,gx,gy;
	cin>>sx>>sy>>gx>>gy;
	sx--;sy--;gx--;gy--;
	vector<string> mp(h);
	lp(i,h)cin>>mp[i];
	queue<pair<int,int>> q;
	vector<vector<int>> dp,mpstate,mpsyoko;
	vector<vector<int>> tate,yoko;
	lp(i,h){
		vector<int> dpb(w,100000000000000),dpbs(w,0);
		dp.push_back(dpb);
		mpstate.push_back(dpbs);
		mpsyoko.push_back(dpbs);
		vector<int> vb(w,-1),vbs(w,-1);
		tate.push_back(vb);
		yoko.push_back(vbs);
	}
	lp(i,h){
		lp(j,w){
			if(j==0)continue;
			if(mp[i][j]=='@'){
				mpsyoko[i][j]=mpsyoko[i][j-1]+1;
			}
			else mpsyoko[i][j]=mpsyoko[i][j-1];
		}
	}
	lp(i,h){
		if(i==0)continue;
		lp(j,w){
			if(mp[i][j]=='@'){
				mpstate[i][j]=mpstate[i-1][j]+1;
			}
			else mpstate[i][j]=mpstate[i-1][j];
		}
	}
	dp[sx][sy]=0;
	q.push({sx,sy});
	while(!q.empty()){
		int nx=q.front().first;
		int ny=q.front().second;
		int cost=dp[nx][ny];
		q.pop();
		//cout<<nx<<" "<<ny<<" "<<cost<<endl;
		cost++;
		tate[nx][ny]=nx;
		yoko[nx][ny]=ny;
		int disx=nx;
		int disy=ny;
		for(int i=nx+1;i<h;i++){
			if(i-nx>k)break;
			if(mpstate[nx][ny]!=mpstate[i][ny])break;
			if(mp[i][ny]=='@')break;
			if(tate[i][ny]!=-1){
				int d=tate[i][ny];
				if(d>=i)break;
				else{
					int gd=d+k;
					if(i<gd){
						i=gd;
						continue;
					}
				}
			}
			if(dp[i][ny]<=cost)continue;
			dp[i][ny]=cost;
			tate[i][ny]=nx;
			q.push({i,ny});
		}
		for(int i=nx-1;i>=0;i--){
			if(nx-i>k)break;
			if(mpstate[nx][ny]!=mpstate[i][ny])break;
			if(mp[i][ny]=='@')break;			
			if(tate[i][ny]!=-1){
				int d=tate[i][ny];
				if(d<=i)break;
				else{
					int gd=d-k;
					if(i>gd){
						i=gd;
						continue;
					}
				}
			}
			if(dp[i][ny]<=cost)continue;
			dp[i][ny]=cost;
			tate[i][ny]=nx;
			q.push({i,ny});
		}
		for(int i=ny+1;i<w;i++){
			if(i-ny>k)break;
			if(mpsyoko[nx][i]!=mpsyoko[nx][ny])break;
			if(mp[nx][i]=='@')break;
			if(yoko[nx][i]!=-1){
				int d=yoko[nx][i];
				if(d>=i)break;
				else{
					int gd=d+k;
					if(i<gd){
						i=gd;
						continue;
					}
				}
			}
			if(dp[nx][i]<=cost)continue;
			dp[nx][i]=cost;
			yoko[nx][i]=ny;
			q.push({nx,i});
		}
		for(int i=ny-1;i>=0;i--){
			if(ny-i>k)break;
			if(mpsyoko[nx][i]!=mpsyoko[nx][ny])break;
			if(mp[nx][i]=='@')break;			
			if(yoko[nx][i]!=-1){
				int d=yoko[nx][i];
				if(d<=i)break;
				else{
					int gd=d-k;
					if(i>gd){
						i=gd;
						continue;
					}
				}
			}
			if(dp[nx][i]<=cost)continue;
			dp[nx][i]=cost;
			yoko[nx][i]=ny;
			q.push({nx,i});
		}
	}
	//cout<<dp<<endl;
	if(dp[gx][gy]==100000000000000)cout<<-1<<endl;
	else cout<<dp[gx][gy]<<endl;
    return 0;
}

Measured memory_bytes: 86464