#include<bits/stdc++.h>
using namespace std;


#define li          long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;

li h, w, k;

string board[1001000];

li dy[] = { -1, 1, 0, 0};
li dx[] = {0, 0, -1, 1};

int main() {
    cin >> h >> w >> k;
    PI s, t;
    cin >> s.F >> s.S >> t.F >> t.S;
    s.F--;
    s.S--;
    t.F--;
    t.S--;

    rep(i, h) {
        cin >> board[i];
    }

    vector<vector<li>> cost(h, vector<li>(w, INF));
    vector<vector<bool>> visited(h, vector<bool>(w, false));

    queue<pair<li, PI>> q;
    q.push({0, s});
    while (!q.empty()) {
        li now_cost = q.front().F;
        PI now = q.front().S;
        q.pop();
        if (visited[now.F][now.S]) {
            continue;
        }
        visited[now.F][now.S] = true;
        if (now == t) {
            cout << now_cost << endl;
            return 0;
        }
        rep(dir, 4) {
            repp(len, 1, k + 1) {
                PI next = {now.F + dy[dir]*len, now.S + dx[dir]*len};
                //p4(now.F, now.S, next.F, next.S);
                if (min(next.F, next.S) < 0 || next.F >= h || next.S >= w) {
                    break;
                }
                if (board[next.F][next.S] == '@') {
                    break;
                }
                if (cost[next.F][next.S] <= now_cost) {
                    break;
                }
                cost[next.F][next.S] = now_cost + 1;
                q.push({now_cost + 1, next});
            }
        }
    }
    puts("-1");

    return 0;
}

Measured memory_bytes: 51296