#[macro_export]
macro_rules !read_value {($iter :expr ,($($t :tt ) ,*) ) =>{($(read_value !($iter ,$t ) ) ,*) } ;($iter :expr ,[$t :tt ;$len :expr ] ) =>{(0 ..$len ) .map (|_ |read_value !($iter ,$t ) ) .collect ::<Vec <_ >>() } ;($iter :expr ,{$t :tt =>$f :expr } ) =>{$f (read_value !($iter ,$t ) ) } ;($iter :expr ,chars ) =>{read_value !($iter ,String ) .chars () .collect ::<Vec <char >>() } ;($iter :expr ,usize1 ) =>{read_value !($iter ,usize ) -1 } ;($iter :expr ,$t :ty ) =>{$iter .next () .unwrap () .parse ::<$t >() .unwrap () } ;}
#[macro_export]
macro_rules !input_inner {($iter :expr ) =>{} ;($iter :expr ,) =>{} ;($iter :expr ,mut $var :ident :$t :tt $($r :tt ) *) =>{let mut $var =read_value !($iter ,$t ) ;input_inner !{$iter $($r ) *} } ;($iter :expr ,mut $var :ident $($r :tt ) *) =>{input_inner !{$iter ,mut $var :usize $($r ) *} } ;($iter :expr ,$var :ident :$t :tt $($r :tt ) *) =>{let $var =read_value !($iter ,$t ) ;input_inner !{$iter $($r ) *} } ;($iter :expr ,$var :ident $($r :tt ) *) =>{input_inner !{$iter ,$var :usize $($r ) *} } ;}
#[macro_export]
macro_rules !input {(source =$s :expr ,$($r :tt ) *) =>{let mut iter =$s .split_whitespace () ;input_inner !{iter ,$($r ) *} } ;(iter =$iter :ident ,$($r :tt ) *) =>{let s ={use std ::io ::Read ;let mut s =String ::new () ;std ::io ::stdin () .read_to_string (&mut s ) .unwrap () ;s } ;let mut $iter =s .split_whitespace () ;input_inner !{$iter ,$($r ) *} } ;($($r :tt ) *) =>{let s ={use std ::io ::Read ;let mut s =String ::new () ;std ::io ::stdin () .read_to_string (&mut s ) .unwrap () ;s } ;let mut iter =s .split_whitespace () ;input_inner !{iter ,$($r ) *} } ;}
fn main() {
    #[allow(unused_imports)]
    use std::io::Write as _;
    let __out = std::io::stdout();
    #[allow(unused_mut, unused_variables)]
    let mut __out = std::io::BufWriter::new(__out.lock());
    #[allow(unused_macros)]
    macro_rules !print {($($arg :tt ) *) =>(::std ::write !(__out ,$($arg ) *) .unwrap () ) }
    #[allow(unused_macros)]
    macro_rules !println {($($arg :tt ) *) =>(::std ::writeln !(__out ,$($arg ) *) .unwrap () ) }
    #[allow(unused_macros)]
    macro_rules! echo {
        ($iter :expr ) => {
            echo!($iter, "\n")
        };
        ($iter :expr ,$sep :expr ) => {
            let mut iter = $iter;
            if let Some(item) = iter.next() {
                print!("{}", item);
            }
            for item in iter {
                print!("{}{}", $sep, item);
            }
            println!();
        };
    }
    input!(
        h,
        w,
        k,
        s: (usize1, usize1),
        t: (usize1, usize1),
        b: [chars; h]
    );
    fn fff(i: &mut usize, x: usize) {
        if *i == !0 {
            *i = x;
        } else if *i < x {
            *i = x;
        }
    }
    let mut que = std::collections::VecDeque::new();
    let mut cost = vec![vec![!0; w]; h];
    let mut cache = vec![vec![(!0, !0, !0, !0); w]; h];
    cost[s.0][s.1] = 0;
    que.push_back(s);
    'o: while let Some((x, y)) = que.pop_front() {
        if (x, y) == t {
            break;
        }
        let c = cost[x][y] + 1;
        {
            let mut v = vec![];
            let mut i = if cache[x][y].0 == !0 {
                1
            } else {
                cache[x][y].0
            };
            while i <= k && x >= i {
                let nx = x - i;
                let ny = y;
                if b[nx][ny] == '@' {
                    break;
                }
                if cache[nx][ny].0 != !0 {
                    i += cache[nx][ny].0;
                    continue;
                }
                if cost[nx][ny] == !0 {
                    cost[nx][ny] = c;
                    if (nx, ny) == t {
                        break 'o;
                    }
                    que.push_back((nx, ny));
                }
                v.push(i);
                i += 1;
            }
            for &j in &v {
                cache[x - j][y].0 = i - j;
                let z = if cache[x][y].1 == !0 {
                    1
                } else {
                    cache[x][y].1
                } + j;
                fff(&mut cache[x - j][y].1, z);
            }
        }
        {
            let mut v = vec![];
            let mut i = if cache[x][y].1 == !0 {
                1
            } else {
                cache[x][y].1
            };
            while i <= k && x + i < h {
                let nx = x + i;
                let ny = y;
                if b[nx][ny] == '@' {
                    break;
                }
                if cache[nx][ny].1 != !0 {
                    i += cache[nx][ny].1;
                    continue;
                }
                if cost[nx][ny] == !0 {
                    cost[nx][ny] = c;
                    if (nx, ny) == t {
                        break 'o;
                    }
                    que.push_back((nx, ny));
                }
                v.push(i);
                i += 1;
            }
            for &j in &v {
                cache[x + j][y].1 = i - j;
                let z = if cache[x][y].0 == !0 {
                    1
                } else {
                    cache[x][y].0
                } + j;
                fff(&mut cache[x + j][y].0, z);
            }
        }
        {
            let mut v = vec![];
            let mut i = if cache[x][y].2 == !0 {
                1
            } else {
                cache[x][y].2
            };
            while i <= k && y >= i {
                let nx = x;
                let ny = y - i;
                if b[nx][ny] == '@' {
                    break;
                }
                if cache[nx][ny].2 != !0 {
                    i += cache[nx][ny].2;
                    continue;
                }
                if cost[nx][ny] == !0 {
                    cost[nx][ny] = c;
                    if (nx, ny) == t {
                        break 'o;
                    }
                    que.push_back((nx, ny));
                }
                v.push(i);
                i += 1;
            }
            for &j in &v {
                cache[x][y - j].2 = i - j;
                let z = if cache[x][y].3 == !0 {
                    1
                } else {
                    cache[x][y].3
                } + j;
                fff(&mut cache[x][y - j].3, z);
            }
        }
        {
            let mut v = vec![];
            let mut i = if cache[x][y].3 == !0 {
                1
            } else {
                cache[x][y].3
            };
            while i <= k && y + i < w {
                let nx = x;
                let ny = y + i;
                if b[nx][ny] == '@' {
                    break;
                }
                if cache[nx][ny].3 != !0 {
                    i += cache[nx][ny].3;
                    continue;
                }
                if cost[nx][ny] == !0 {
                    cost[nx][ny] = c;
                    if (nx, ny) == t {
                        break 'o;
                    }
                    que.push_back((nx, ny));
                }
                v.push(i);
                i += 1;
            }
            for &j in &v {
                cache[x][y + j].3 = i - j;
                let z = if cache[x][y].2 == !0 {
                    1
                } else {
                    cache[x][y].2
                } + j;
                fff(&mut cache[x][y + j].2, z);
            }
        }
    }
    println!(
        "{}",
        if cost[t.0][t.1] == !0 {
            -1
        } else {
            cost[t.0][t.1]
        }
    );
}


Measured memory_bytes: 44684