#![allow(unused_imports)]

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String {
            bytes
                .by_ref()
                .map(|r| r.unwrap() as char)
                .skip_while(|c| c.is_whitespace())
                .take_while(|c| !c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, [ $t:tt ]) => {
        {
            let len = read_value!($next, usize);
            (0..len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
        }
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

use std::cmp::{min, max};
use std::collections::{HashMap, HashSet, VecDeque, BinaryHeap};

fn main() {
    input!{
        h: usize,
        w: usize,
        k: usize,
        s: (usize1, usize1),
        t: (usize1, usize1),
        v: [chars; h]
    }
    if let Some(ans) = dijkstra(s, t, k, &v) {
        println!("{}", ans);
    } else {
        println!("-1");
    }
}

use std::cmp::Ordering;

#[derive(Debug, PartialEq, Eq)]
struct State(usize, usize, usize);

impl Ord for State {
    fn cmp(&self, other: &Self) -> Ordering {
        other.2.cmp(&self.2)
    }
}

impl PartialOrd for State {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

fn dijkstra(s: (usize, usize), t: (usize, usize), k: usize, v: &Vec<Vec<char>>) -> Option<usize> {
    let h = v.len();
    let w = v[0].len();
    let mut pq = BinaryHeap::new();
    pq.push(State(s.0, s.1, 0));
    let mut dist = vec![usize::max_value(); h * w];
    dist[s.0 * w + s.1] = 0;
    while let Some(st) = pq.pop() {
        if st.0 == t.0 && st.1 == t.1 {
            return Some(st.2);
        }
        let d = st.2 + 1;
        for i in 1..k + 1 {
            if i > st.0 || v[st.0 - i][st.1] == '@' {
                break;
            }
            let x = st.0 - i;
            let y = st.1;
            if dist[x * w + y] > d {
                dist[x * w + y] = d;
                pq.push(State(x, y, d));
            } else if dist[x * w + y] <= st.2 {
                break;
            }
        }
        for i in 1..k + 1 {
            if i > st.1 || v[st.0][st.1 - i] == '@' {
                break;
            }
            let x = st.0;
            let y = st.1 - i;
            if dist[x * w + y] > d {
                dist[x * w + y] = d;
                pq.push(State(x, y, d));
            } else if dist[x * w + y] <= st.2 {
                break;
            }
        }
        for i in 1..k + 1 {
            if st.0 + i >= h || v[st.0 + i][st.1] == '@' {
                break;
            }
            let x = st.0 + i;
            let y = st.1;
            if dist[x * w + y] > d {
                dist[x * w + y] = d;
                pq.push(State(x, y, d));
            } else if dist[x * w + y] <= st.2 {
                break;
            }
        }
        for i in 1..k + 1 {
            if st.1 + i >= w || v[st.0][st.1 + i] == '@' {
                break;
            }
            let x = st.0;
            let y = st.1 + i;
            if dist[x * w + y] > d {
                dist[x * w + y] = d;
                pq.push(State(x, y, d));
            } else if dist[x * w + y] <= st.2 {
                break;
            }
        }
    }
    None
}


Measured memory_bytes: 16512