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

using pii = pair<int, int>;
const int N = 3030;

int r, c, n;

string g[N];
vector<int> d[N], nxt[N], nxtR[N];
deque<pii> q;

void record(int x, int y, int z) {
    if(x < 0 || x >= r || y < 0 || y >= c || g[x][y] != '.' || d[x][y] != -1) return;
    d[x][y] = z;
    q.emplace_front(x, y);
}

int findR(int x, int y) {
    return nxtR[x][y] == x ? x : nxtR[x][y] = findR(nxtR[x][y], y);
}

int findC(int x, int y) {
    return nxt[x][y] == y ? y : nxt[x][y] = findC(x, nxt[x][y]);
}

void stamp(int x, int y, int z) {
    x = min(max(x, 0), r - 1);
    y = min(max(y, 0), c - 1);
    for(int i = findR(x, y); i < r && i - x < n; i = nxtR[i][y] = findR(i + 1, y))
        for(int j = findC(i, y); j < c && j - y < n; j = nxt[i][j] = findC(i, j + 1)) {
            d[i][j] = z + 1;
            q.emplace_back(i, j);
        }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> r >> c >> n;
    int sr, sc, tr, tc;
    cin >> sr >> sc >> tr >> tc;
    for(int i = 0; i < r; i ++) {
        cin >> g[i];
        d[i] = vector<int>(c, -1);
        nxt[i] = vector<int>(c + 1, c);
        nxtR[i] = vector<int>(c, r);
    }
    nxtR[r] = vector<int>(c, r);

    for(int i = 0; i < r; i ++)
        for(int j = c - 1; j >= 0; j --) {
            nxt[i][j] = g[i][j] == '#' ? j : nxt[i][j + 1];
            nxtR[i][j] = i;
        }

    sr --;
    sc --;
    tr --;
    tc --;
    d[sr][sc] = 0;
    
    q.emplace_back(sr, sc);
    while(q.size()) {
        auto [x, y] = q.front();
        q.pop_front();

        record(x, y - 1, d[x][y]);
        record(x - 1, y, d[x][y]);
        record(x, y + 1, d[x][y]);
        record(x + 1, y, d[x][y]);
        
        stamp(x - (n - 1), y - n, d[x][y]);
        stamp(x - n, y - (n - 1), d[x][y]);
        stamp(x, y - n, d[x][y]);
        stamp(x + 1, y - (n - 1), d[x][y]);
        stamp(x - (n - 1), y + 1, d[x][y]);
        stamp(x - n, y, d[x][y]);
        stamp(x, y + 1, d[x][y]);
        stamp(x + 1, y, d[x][y]);
    }

    cout << d[tr][tc] << "\n";
}