#include <bits/stdc++.h>
 
#define FOR(i, a, b) for(auto i=a; i<=b; ++i)
#define REP(i, a, b) for(auto i=a; i<b; ++i)
#define FORI(i, a, b) for(auto i=a; i!=b+1-2*(a>b); i+=1-2*(a>b))
#define REPI(i, a, b) for(auto i=a-(a>b); i!=b-(a>b); i+=1-2*(a>b))
#define ALL(v) v.begin(),v.end()
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define pf(a) push_front(a)
#define eb(a, b) emplace_back(a, b)
#define fir first
#define sec second
#define what_is(x) cout<<#x<<" is "<<x<<endl;
#define type(x) typeid(x).name()
#define ms(arr, val) memset(arr, val, sizeof(arr))
#define min3(a,b,c) min(min(a,b),c)
#define max3(a,b,c) max(max(a,b),c)
#define PI acos(-1)
#define open_read freopen("christmas.in", "r", stdin)
#define open_write freopen("christmas.out", "w", stdout)
 
using namespace std;
 
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
typedef pair<double, double> PDD;
typedef pair<int, int> PII;
typedef pair<int, PII> PIPII;
typedef pair<PII, PII> PPIIPII;
typedef pair<LL, LL> PLL;
typedef pair<ULL, ULL> PUU;
typedef pair<LL, PLL> PLPLL;
typedef pair<PLL, PLL> PPLLPLL;
typedef pair<int, LL> PIL;
typedef pair<LL, int> PLI;
 
template<typename T, typename T1>
ostream& operator << (ostream &out, pair<T, T1> obj) {
    out << "(" << obj.first << ", " << obj.second << ")";
    return out;
}
 
template<typename T, typename T1>
ostream& operator << (ostream &out, map<T, T1> cont) {
    typename map<T, T1>::const_iterator itr = cont.begin();
    typename map<T, T1>::const_iterator ends = cont.end();
 
    for(; itr != ends; ++itr) {
        out << *itr << " ";
    }
 
    out<<endl;
    return out;
} 

template<typename T>
ostream& operator << (ostream &out, set<T> cont) {
    typename set<T>::const_iterator itr = cont.begin();
    typename set<T>::const_iterator ends = cont.end();
    
    for(; itr != ends; ++itr) {
        out << *itr << " ";
    }
 
    out << endl;
    return out;
}
  
template<typename T>
ostream& operator << (ostream &out, multiset<T> cont) {
    typename multiset<T>::const_iterator itr = cont.begin();
    typename multiset<T>::const_iterator ends = cont.end();
 
    for (; itr != ends; ++itr) {
        out << *itr << " ";
    }
 
    out << endl;
    return out;
}

template<typename T, template<typename ELEM, typename ALLOC=allocator<ELEM>> class CONT>
ostream& operator << (ostream &out, CONT<T> cont) {
    typename CONT<T>::const_iterator itr = cont.begin();
    typename CONT<T>::const_iterator ends = cont.end();
 
    for (; itr != ends; ++itr) {
        out << *itr << " ";
    }
 
    out << endl;
    return out;
}
 
template<typename T, unsigned int N, typename CTy, typename CTr>
typename enable_if<!is_same<T, char>::value, basic_ostream<CTy, CTr> &>::type
operator << (basic_ostream<CTy, CTr> &out, const T (&arr)[N]) {
    REP (i, 0, N) {
        out << arr[i] << " ";
    }
 
    out << endl;
    return out;
}
  
template<typename T>
T GCD(T a, T b) {
    T min_v = min(a, b);
    T max_v = max(a, b);
 
    while (min_v) {
        T temp = max_v % min_v;
        max_v = min_v;
        min_v = temp;
    }
 
    return max_v;
}
 
template<typename T>
T LCM(T a, T b) {
    return (a * b) / gcd(a, b);
}
 
template<typename T>
T fastExpPow(T base, T exp, T mod) {
    T res = 1;
 
    while (exp) {
        if (exp & 1) {
            res *= base;
            res %= mod;
        }
 
        exp >>= 1;
        base *= base;
        base %= mod;
    }
 
    return res % mod;
}
 
/*#################################################################################################################
###################################################################################################################
###################################################################################################################
#################################################################################################################*/

#define SIZE 1000010

int H, W, K, X1, Y1, X2, Y2;
vector<char> board[SIZE];
map<PIPII, int> minDist;
queue<PIPII> que;


bool invalid(PII pos) {
    return pos.fir >= H || pos.fir < 0 || pos.sec >= W || pos.sec < 0 || board[pos.fir][pos.sec] == '@';
}

void bfs() {
    que.push(mp(0, mp(X1, Y1)));
    que.push(mp(1, mp(X1, Y1)));
    minDist[mp(0, mp(X1, Y1))] = 0;
    minDist[mp(1, mp(X1, Y1))] = 0;

    while (!que.empty()) {
        int type = que.front().fir;
        PII pos = que.front().sec;
        que.pop();

        int currDist = minDist[mp(type, pos)];
        
        FOR (t, 0, 1) {
            for (int dir = -1; dir <= 1; dir += 2) {
                FOR (i, 1, K) {
                    PII newPos = mp(pos.fir + i * dir * (int)(t == 0), pos.sec + i * dir * (int)(t == 1));
                    
                    if (minDist.count(mp(t, newPos)) || invalid(newPos)) {
                        break;
                    }

                    if (minDist.count(mp(1 - t, newPos)) && minDist[mp(1 - t, newPos)] <= currDist) {
                        break;
                    }

                    minDist[mp(t, newPos)] = currDist + 1;
                    que.push(mp(t, newPos));
                }
            }
        }
    }
}


int main() {   
    scanf("%d%d%d%d%d%d%d", &H, &W, &K, &X1, &Y1, &X2, &Y2);
    --X1, --Y1, --X2, --Y2;
    
    REP (i, 0, H) {
        REP (j, 0, W) {
            char ch;
            scanf(" %c", &ch);
            board[i].pb(ch);
        }
    }
    
    bfs(); 
    int answer = -1;
    
    FOR (t, 0, 1) {
        if (minDist.count(mp(t, mp(X2, Y2)))) {
            answer = (answer == -1 ? minDist[mp(t, mp(X2, Y2))] : min(answer, minDist[mp(t, mp(X2, Y2))]));
        }
    }

    printf("%d\n", answer);
    return 0;
}  


Measured memory_bytes: 97708