#![allow(unused_imports)]
#![allow(non_snake_case, unused)]

use std::cmp::*;
use std::collections::*;
use std::ops::*;

// https://atcoder.jp/contests/hokudai-hitachi2019-1/submissions/10518254

macro_rules! eprint {
	($($t:tt)*) => {{
		use ::std::io::Write;
		let _ = write!(::std::io::stderr(), $($t)*);
	}};
}
macro_rules! eprintln {
	() => { eprintln!(""); };
	($($t:tt)*) => {{
		use ::std::io::Write;
		let _ = writeln!(::std::io::stderr(), $($t)*);
	}};
}
macro_rules! dbg {
	($v:expr) => {{
		let val = $v;
		eprintln!("[{}:{}] {} = {:?}", file!(), line!(), stringify!($v), val);
		val
	}}
}

macro_rules! mat {
	($($e:expr),*) => { Vec::from(vec![$($e),*]) };
	($($e:expr,)*) => { Vec::from(vec![$($e),*]) };
	($e:expr; $d:expr) => { Vec::from(vec![$e; $d]) };
	($e:expr; $d:expr $(; $ds:expr)+) => { Vec::from(vec![mat![$e $(; $ds)*]; $d]) };
}

macro_rules! ok {
	($a:ident$([$i:expr])*.$f:ident()$(@$t:ident)*) => {
		$a$([$i])*.$f($($t),*)
	};
	($a:ident$([$i:expr])*.$f:ident($e:expr$(,$es:expr)*)$(@$t:ident)*) => { {
		let t = $e;
		ok!($a$([$i])*.$f($($es),*)$(@$t)*@t)
	} };
}

pub fn readln() -> String {
	let mut line = String::new();
	::std::io::stdin().read_line(&mut line).unwrap_or_else(|e| panic!("{}", e));
	line
}

macro_rules! read {
	($($t:tt),*; $n:expr) => {{
		let stdin = ::std::io::stdin();
		let ret = ::std::io::BufRead::lines(stdin.lock()).take($n).map(|line| {
			let line = line.unwrap();
			let mut it = line.split_whitespace();
			_read!(it; $($t),*)
		}).collect::<Vec<_>>();
		ret
	}};
	($($t:tt),*) => {{
		let line = readln();
		let mut it = line.split_whitespace();
		_read!(it; $($t),*)
	}};
}

macro_rules! _read {
	($it:ident; [char]) => {
		_read!($it; String).chars().collect::<Vec<_>>()
	};
	($it:ident; [u8]) => {
		Vec::from(_read!($it; String).into_bytes())
	};
	($it:ident; usize1) => {
		$it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1
	};
	($it:ident; [usize1]) => {
		$it.map(|s| s.parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1).collect::<Vec<_>>()
	};
	($it:ident; [$t:ty]) => {
		$it.map(|s| s.parse::<$t>().unwrap_or_else(|e| panic!("{}", e))).collect::<Vec<_>>()
	};
	($it:ident; $t:ty) => {
		$it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<$t>().unwrap_or_else(|e| panic!("{}", e))
	};
	($it:ident; $($t:tt),+) => {
		($(_read!($it; $t)),*)
	};
}


pub fn main() {
	let _ = ::std::thread::Builder::new().name("run".to_string()).stack_size(32 * 1024 * 1024).spawn(run).unwrap().join();
}

const MOD: u32 = 1_000_000_007;
const INF: usize = std::usize::MAX/3;

fn solve() {
	let (h,w,k) = read!(usize,usize,usize);
	let (sx,sy,tx,ty) = read!(usize,usize,usize,usize);
	let board = read!([char];h);
	let mut q = BinaryHeap::new();
	q.push(Reverse((0,sx-1,sy-1,4)));
	let mut dist = vec![vec![vec![INF;5];w];h];
	dist[sx-1][sy-1][4] = 0;
	let dir = [(1,0),(0,1),(-1,0),(0,-1)];
	while let Some(Reverse((cd,cx,cy,cdir))) = q.pop() {
		for (ndir,&(dx,dy)) in dir.iter().enumerate() {
			let nx = cx.wrapping_add(dx as usize);
			let ny = cy.wrapping_add(dy as usize);
			if nx>=h || ny>=w {
				continue;
			}
			if board[nx][ny]=='@' {
				continue;
			}
			if ndir==cdir || ndir==4 {
				let nd = cd + 1;
				if nd < dist[nx][ny][ndir] {
					dist[nx][ny][ndir] = nd;
					q.push(Reverse((nd,nx,ny,ndir)));
				}
			}
			else {
				let nd = (cd+k-1)/k*k + 1;
				if nd < dist[nx][ny][ndir] {
					dist[nx][ny][ndir] = nd;
					q.push(Reverse((nd,nx,ny,ndir)));
				}
			}
		}
	}
	let ans = dist[tx-1][ty-1].iter().cloned().min().unwrap();
	match ans {
		INF => println!("-1"),
		_ => println!("{}",(ans+k-1)/k),
	}
}

fn run() {
    solve();
}


Measured memory_bytes: 83560