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")
    };
}

#[allow(unused_imports)]
use std::cmp::{min, max};
use std::collections::VecDeque;

fn main() {
    input!{
        h: usize,
        w: usize,
        k: usize,
        v: [chars; h]
    }
    let mut q = VecDeque::new();
    let mut dist = vec![vec![usize::max_value(); w]; h];
    let mut s = (0, 0);
    'outer: for i in 0..h {
        for j in 0..w {
            if v[i][j] == 'S' {
                s = (i, j);
                break 'outer;
            }
        }
    }
    dist[s.0][s.1] = 0;
    q.push_back(s);
    while let Some((i, j)) = q.pop_front() {
        if i == 0 || i == h - 1 || j == 0 || j == w - 1 {
            println!("1");
            return;
        }
        if dist[i][j] == k {
            continue;
        }
        if v[i][j + 1] == '.' && dist[i][j + 1] > dist[i][j] + 1 {
            dist[i][j + 1] = dist[i][j] + 1;
            q.push_back((i, j + 1));
        }
        if v[i][j - 1] == '.' && dist[i][j - 1] > dist[i][j] + 1 {
            dist[i][j - 1] = dist[i][j] + 1;
            q.push_back((i, j - 1));
        }
        if v[i + 1][j] == '.' && dist[i + 1][j] > dist[i][j] + 1 {
            dist[i + 1][j] = dist[i][j] + 1;
            q.push_back((i + 1, j));
        }
        if v[i - 1][j] == '.' && dist[i - 1][j] > dist[i][j] + 1 {
            dist[i - 1][j] = dist[i][j] + 1;
            q.push_back((i - 1, j));
        }
    }
    for i in 0..h {
        for j in 0..w {
            if dist[i][j] < usize::max_value() {
                dist[i][j] = k;
                q.push_back((i, j));
            }
        }
    }
    while let Some((i, j)) = q.pop_front() {
        if i == 0 || i == h - 1 || j == 0 || j == w - 1 {
            println!("{}", (dist[i][j] + k - 1) / k);
            return;
        }
        if j < w - 1 && dist[i][j + 1] > dist[i][j] + 1 {
            dist[i][j + 1] = dist[i][j] + 1;
            q.push_back((i, j + 1));
        }
        if j > 0 && dist[i][j - 1] > dist[i][j] + 1 {
            dist[i][j - 1] = dist[i][j] + 1;
            q.push_back((i, j - 1));
        }
        if i < h - 1 && dist[i + 1][j] > dist[i][j] + 1 {
            dist[i + 1][j] = dist[i][j] + 1;
            q.push_back((i + 1, j));
        }
        if i > 0 && dist[i - 1][j] > dist[i][j] + 1 {
            dist[i - 1][j] = dist[i][j] + 1;
            q.push_back((i - 1, j));
        }
    }
}


Measured memory_bytes: 12540