use std::cmp::*;
use input_mcr::*;
use std::collections::VecDeque;
use field::*;

fn main() {
    input! {
        h: usize,
        w: usize,
        d: usize,
        sy: usize1,
        sx: usize1,
        ty: usize1,
        tx: usize1,
        field: [chars; h],
    }
    let s = Pos{x:sx,y:sy};
    let t = Pos{x:tx,y:ty};
    let field = Field::from_vec_vec(&field);
    let inf = 1i64 << 50;
    let mut dist = Field::<i64>::new(h,w,inf);
    dist[s] = 0;
    let mut q = VecDeque::new();
    q.push_back(s);
    while let Some(p) = q.pop_front() {
        for &dir in &DIRS {
            for p2 in field.nexts(p, dir).take(d) {
                if field[p2] == '@' {
                    break;
                }
                if dist[p2] > dist[p] + 1 {
                    dist[p2] = dist[p] + 1;
                    q.push_back(p2);
                }
                if dist[p2] <= dist[p] {
                    break;
                }
            }
        }
    }
    let res = dist[t];
    if res >= inf / 2 {
        println!("-1");
    } else {
        println!("{}", res);
    }
}
pub mod input_mcr {
    // ref: tanakh <https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8>
    #[macro_export(local_inner_macros)]
    macro_rules! input {
        (source = $s:expr, $($r:tt)*) => {
            let mut parser = Parser::from_str($s);
            input_inner!{parser, $($r)*}
        };
        (parser = $parser:ident, $($r:tt)*) => {
            input_inner!{$parser, $($r)*}
        };
        (new_stdin_parser = $parser:ident, $($r:tt)*) => {
            let stdin = std::io::stdin();
            let reader = std::io::BufReader::new(stdin.lock());
            let mut $parser = Parser::new(reader);
            input_inner!{$parser, $($r)*}
        };
        ($($r:tt)*) => {
            input!{new_stdin_parser = parser, $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! input_inner {
        ($parser:ident) => {};
        ($parser:ident, ) => {};
        ($parser:ident, $var:ident : $t:tt $($r:tt)*) => {
            let $var = read_value!($parser, $t);
            input_inner!{$parser $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! read_value {
        ($parser:ident, ( $($t:tt),* )) => {
            ( $(read_value!($parser, $t)),* )
        };
        ($parser:ident, [ $t:tt ; $len:expr ]) => {
            (0..$len).map(|_| read_value!($parser, $t)).collect::<Vec<_>>()
        };
        ($parser:ident, chars) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()
        };
        ($parser:ident, char_) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()[0]
        };
        ($parser:ident, usize1) => {
            read_value!($parser, usize) - 1
        };
        ($parser:ident, line) => {
            $parser.next_line()
        };
        ($parser:ident, line_) => {
            $parser.next_line().chars().collect::<Vec<char>>()
        };
        ($parser:ident, $t:ty) => {
            $parser.next::<$t>().expect("Parse error")
        };
    }
    
    use std::io;
    use std::io::BufRead;
    use std::str;
    use std::collections::VecDeque;
    
    pub struct Parser<R> {
        pub reader: R,
        buf: VecDeque<u8>,
        parse_buf: Vec<u8>,
    }
    
    impl Parser<io::Empty> {
        pub fn from_str(s: &str) -> Parser<io::Empty> {
            Parser {
                reader: io::empty(),
                buf: VecDeque::from(s.as_bytes().to_vec()),
                parse_buf: vec![],
            }
        }
    }
    
    impl<R: BufRead> Parser<R> {
        pub fn new(reader: R) -> Parser<R> {
            Parser {
                reader: reader,
                buf: VecDeque::new(),
                parse_buf: vec![],
            }
        }
        pub fn update_buf(&mut self) {
            loop {
                let (len, complete) = {
                    let buf2 = self.reader.fill_buf().unwrap();
                    self.buf.extend(buf2.iter());
                    let len = buf2.len();
                    (len, buf2.last() < Some(&0x20))
                };
                self.reader.consume(len);
                if complete {
                    break;
                }
            }
        }
        pub fn next<T: str::FromStr>(&mut self) -> Result<T, T::Err> {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c > 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c <= 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.parse::<T>();
                }
            }
        }
        pub fn next_line(&mut self) -> String {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c >= 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c < 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.to_string();
                }
            }
        }
    }
}
pub mod field {
    use std::ops::{Index,IndexMut};
    use std::iter::Iterator;
    
    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
    pub enum Dir {
        U,
        R,
        D,
        L,
    }
    
    pub const DIRS: [Dir; 4] = [Dir::U, Dir::R, Dir::D, Dir::L];
    
    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Default, Hash)]
    pub struct Pos {
        pub x: usize,
        pub y: usize,
    }
    
    pub struct Field<T> {
        h: usize,
        w: usize,
        field: Vec<T>,
    }
    
    pub struct N4 {
        i: usize,
        x: usize,
        y: usize,
        h: usize,
        w: usize,
    }
    
    impl Iterator for N4 {
        type Item = Pos;
        fn next(&mut self) -> Option<Pos> {
            let dx = [0, 1, 0, -1];
            let dy = [-1, 0, 1, 0];
            while self.i < 4 {
                let nx = self.x as i64 + dx[self.i];
                let ny = self.y as i64 + dy[self.i];
                if 0 <= nx && nx < self.w as i64 && 0 <= ny && ny < self.h as i64 {
                    self.i += 1;
                    return Some(Pos {
                        x: nx as usize,
                        y: ny as usize,
                    });
                }
                self.i += 1;
            }
            None
        }
    }
    
    pub struct Nexts<'a,T> {
        field: &'a Field<T>,
        pos: Pos,
        dir: Dir,
    }
    
    impl<'a,T:Clone+Copy+Default> Iterator for Nexts<'a,T> {
        type Item = Pos;
        fn next(&mut self) -> Option<Pos> {
            let pos2 = self.field.next(self.pos, self.dir);
            if let Some(pos2) = pos2 {
                self.pos = pos2;
                Some(pos2)
            } else {
                None
            }
        }
    }
    
    impl<T:Clone+Copy+Default> Field<T> {
        pub fn new(h: usize, w: usize, default: T) -> Field<T> {
            Field::<T> {
                h,
                w,
                field: vec![default; h*w],
            }
        }
        pub fn from_vec_vec(xss: &Vec<Vec<T>>) -> Field<T> {
            let h = xss.len();
            let w = xss[0].len();
            let mut field = vec![];
            for y in 0..h {
                for x in 0..w {
                    field.push(xss[y][x]);
                }
            }
            Field::<T> {
                h,
                w,
                field,
            }
        }
        pub fn n4(&self, pos: Pos) -> N4 {
            N4 {
                i: 0,
                x: pos.x,
                y: pos.y,
                h: self.h,
                w: self.w
            }
        }
        pub fn next(&self, pos: Pos, dir: Dir) -> Option<Pos> {
            match dir {
                Dir::U => {
                    if pos.y > 0 {
                        return Some(Pos {
                            x: pos.x,
                            y: pos.y-1,
                        })
                    }
                }
                Dir::R => {
                    if pos.x+1 < self.w {
                        return Some(Pos {
                            x: pos.x+1,
                            y: pos.y
                        })
                    }
                }
                Dir::D => {
                    if pos.y+1 < self.h {
                        return Some(Pos {
                            x: pos.x,
                            y: pos.y+1,
                        })
                    }
                }
                Dir::L => {
                    if pos.x > 0 {
                        return Some(Pos {
                            x: pos.x-1,
                            y: pos.y,
                        })
                    }
                }
            }
            None
        }
        pub fn nexts<'a>(&'a self, pos: Pos, dir: Dir) -> Nexts<'a, T> {
            Nexts {
                field: self,
                pos,
                dir,
            }
        }
    }
    
    impl<T:Clone+Copy+Default> Index<Pos> for Field<T> {
        type Output = T;
        fn index(&self, pos: Pos) -> &T {
            &self.field[pos.y*self.w+pos.x]
        }
    }
    
    impl<T:Clone+Copy+Default> IndexMut<Pos> for Field<T> {
        fn index_mut(&mut self, pos: Pos) -> &mut T {
            &mut self.field[pos.y*self.w+pos.x]
        }
    }
}



Measured memory_bytes: 20720