use std::cmp::min;
use std::collections::{BTreeSet, BinaryHeap, VecDeque};

const INF: u64 = 1 << 60;

const U: usize = 0;
const D: usize = 1;
const R: usize = 2;
const L: usize = 3;

fn main() {
    let (r, w) = (std::io::stdin(), std::io::stdout());
    let mut sc = IO::new(r.lock(), w.lock());

    let h: usize = sc.read();
    let w: usize = sc.read();
    let k: usize = sc.read();
    let (sx, sy) = (sc.read::<usize>() - 1, sc.read::<usize>() - 1);
    let (tx, ty) = (sc.read::<usize>() - 1, sc.read::<usize>() - 1);
    let board: Vec<Vec<bool>> = (0..h)
        .map(|_| sc.read::<String>().chars().map(|c| c == '.').collect())
        .collect();
    let mut dist = vec![vec![vec![INF; w]; h]; 4];
    let mut rows = vec![vec![BTreeSet::new(); h]; 4];
    let mut cols = vec![vec![BTreeSet::new(); w]; 4];
    let mut row_blocker = vec![BTreeSet::new(); h];
    let mut col_blocker = vec![BTreeSet::new(); w];
    let mut q = VecDeque::new();
    for i in 0..h {
        for j in 0..w {
            if !board[i][j] {
                row_blocker[i].insert(j);
                col_blocker[j].insert(i);
                continue;
            }
            if i == sx && j == sy {
                for d in 0..4 {
                    dist[d][i][j] = 0;
                }
                q.push_back((4, i, j));
            } else {
                for d in 0..4 {
                    rows[d][i].insert(j);
                    cols[d][j].insert(i);
                }
            }
        }
    }

    let mut tmp = VecDeque::new();
    while let Some((prev_d, cur_i, cur_j)) = q.pop_front() {
        let prev_dist = if prev_d < 4 {
            dist[prev_d][cur_i][cur_j]
        } else {
            0
        };
        for next_d in 0..4 {
            match next_d {
                U => {
                    let blocker = col_blocker[cur_j].range(..cur_i).next_back();
                    for &next_i in cols[U][cur_j].range(..cur_i).rev() {
                        if cur_i > next_i + k {
                            break;
                        }
                        if blocker.is_some() && *blocker.unwrap() > next_i {
                            break;
                        }
                        dist[U][next_i][cur_j] = prev_dist + 1;
                        q.push_back((U, next_i, cur_j));
                        tmp.push_back(next_i);
                    }
                    while let Some(next_i) = tmp.pop_back() {
                        assert!(cols[U][cur_j].remove(&next_i));
                        assert!(rows[U][next_i].remove(&cur_j));
                    }
                }
                D => {
                    let blocker = col_blocker[cur_j].range((cur_i + 1)..).next();
                    for &next_i in cols[D][cur_j].range((cur_i + 1)..) {
                        if next_i > cur_i + k {
                            break;
                        }
                        if blocker.is_some() && *blocker.unwrap() < next_i {
                            break;
                        }
                        dist[D][next_i][cur_j] = prev_dist + 1;
                        q.push_back((D, next_i, cur_j));
                        tmp.push_back(next_i);
                    }
                    while let Some(next_i) = tmp.pop_back() {
                        assert!(cols[D][cur_j].remove(&next_i));
                        assert!(rows[D][next_i].remove(&cur_j));
                    }
                }
                R => {
                    let blocker = row_blocker[cur_i].range((cur_j + 1)..).next().cloned();
                    for &next_j in rows[R][cur_i].range((cur_j + 1)..) {
                        if next_j > cur_j + k {
                            break;
                        }
                        if blocker.is_some() && blocker.unwrap() < next_j {
                            break;
                        }
                        dist[R][cur_i][next_j] = prev_dist + 1;
                        q.push_back((R, cur_i, next_j));
                        tmp.push_back(next_j);
                    }
                    while let Some(next_j) = tmp.pop_back() {
                        assert!(rows[R][cur_i].remove(&next_j));
                        assert!(cols[R][next_j].remove(&cur_i));
                    }
                }
                L => {
                    let blocker = row_blocker[cur_i].range(..cur_j).next_back();
                    for &next_j in rows[L][cur_i].range(..cur_j).rev() {
                        if next_j + k < cur_j {
                            break;
                        }
                        if blocker.is_some() && *blocker.unwrap() > next_j {
                            break;
                        }
                        dist[L][cur_i][next_j] = prev_dist + 1;
                        q.push_back((L, cur_i, next_j));
                        tmp.push_back(next_j);
                    }
                    while let Some(next_j) = tmp.pop_back() {
                        assert!(rows[L][cur_i].remove(&next_j));
                        assert!(cols[L][next_j].remove(&cur_i));
                    }
                }
                _ => unreachable!(),
            }
        }
    }

    let mut ans = INF;
    for d in 0..4 {
        ans = min(ans, dist[d][tx][ty]);
    }
    if ans == INF {
        println!("-1");
    } else {
        println!("{}", ans);
    }
}

pub struct IO<R, W: std::io::Write>(R, std::io::BufWriter<W>);

impl<R: std::io::Read, W: std::io::Write> IO<R, W> {
    pub fn new(r: R, w: W) -> Self {
        Self(r, std::io::BufWriter::new(w))
    }
    pub fn write<S: ToString>(&mut self, s: S) {
        use std::io::Write;
        self.1.write(s.to_string().as_bytes()).unwrap();
    }
    pub fn read<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .0
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b' ' || b == b'\n' || b == b'\r' || b == b'\t')
            .take_while(|&b| b != b' ' && b != b'\n' && b != b'\r' && b != b'\t')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read()).collect()
    }
    pub fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
}


Measured memory_bytes: 669100