#include <bits/stdc++.h>

using namespace std;

const int N = 1002;

bool G[N][N];

int n, m, k, d[N][N];

set<int> xs[N], ys[N];

void clear_rem(vector<pair<int,int> > &rem){

    for(auto p : rem){

        xs[p.first].erase(p.second);

        ys[p.second].erase(p.first);

    }

    rem.clear();

}

void bfs(int sx, int sy){

    xs[sx].erase(sy); ys[sy].erase(sx);

    queue<pair<int,int> > q; q.push({sx,sy});

    d[sx][sy]=0;

    while(!q.empty()){

        pair<int,int> u=q.front(); q.pop();

        int x = u.first, y=u.second;

        vector<pair<int,int> > rem;

        for(auto it=xs[x].lower_bound(y); it!=xs[x].end(); it++){

            if(*it-k>y || !G[x][*it])break;

            rem.push_back({x,*it});

            q.push({x,*it}); d[x][*it]=d[x][y]+1;

        }

        clear_rem(rem);

        for(auto it=ys[y].lower_bound(x); it!=ys[y].end(); it++){

            if(*it-k>x || !G[*it][y])break;

            rem.push_back({*it,y});

            q.push({*it,y}); d[*it][y]=d[x][y]+1;

        }

        clear_rem(rem);

        auto it=xs[x].lower_bound(y);

        if(it!=xs[x].begin()){

            it--;

            while(1){

                if(y-*it>k || !G[x][*it])break;

                rem.push_back({x,*it});

                q.push({x,*it}); d[x][*it]=d[x][y]+1;

                if(it==xs[x].begin())break;

                it--;

            }

        }

        clear_rem(rem);

        it=ys[y].lower_bound(x);

        if(it!=ys[y].begin()){

            it--;

            while(1){

                if(x-*it>k || !G[*it][y])break;

                rem.push_back({*it,y});

                q.push({*it,y}); d[*it][y]=d[x][y]+1;

                if(it==ys[y].begin())break;

                it--;

            }

        }

        clear_rem(rem);

    }

}

int main(){ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    memset(d,-1,sizeof(d));

    cin >> n >> m >> k;

    for(int x=1; x<=n; x++)

        for(int y=1; y<=m; y++){

            char c; cin >> c;

            G[x][y]=c=='.';

            xs[x].insert(y);

            ys[y].insert(x);

        }

    int X, Y; cin >> X >> Y;

    bfs(X,Y);

    cin >> X >> Y;

    cout << d[X][Y] << "\n";

}