#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <set>
#include <map>
#include <numeric>
#include <iomanip>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#include <tuple>
#include <cassert>
#include <list>
#include <random>
#include <initializer_list>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
constexpr ld inf = 1e18;
constexpr ll N = 15;
constexpr ll MIN = -inf;
constexpr ll MAX = inf;
vector<ll> dx{ 0, 0, 1, -1 };
vector<ll> dy{ 1, -1, 0, 0 };
struct T {
ll x, y;
};
void solve() {
ll n, k;
cin >> n >> k;
vector<string> a(n);
T s = { MAX, MAX }, f = { MAX, MAX };
for (ll i = 0; i < n; ++i) {
cin >> a[i];
for (ll j = 0; j < n; ++j) {
if (a[i][j] == 'M') {
s = { i, j };
}
else if (a[i][j] == 'D') {
f = { i, j };
}
}
}
queue<T> q;
vector<vector<ll>> dh(n, vector<ll>(n, MAX));
for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
if (a[i][j] == 'H') {
dh[i][j] = 0;
q.push({ i, j });
}
}
}
auto ok = [&](ll x, ll y) -> bool {
return x >= 0 && x < n && y >= 0 && y < n;
};
while (!q.empty()) {
T v = q.front();
q.pop();
for (ll i = 0; i < 4; ++i) {
ll x = v.x + dx[i], y = v.y + dy[i];
if (ok(x, y) && (a[x][y] == 'G' || a[x][y] == 'M') && dh[x][y] == MAX) {
dh[x][y] = dh[v.x][v.y] + 1;
q.push({ x, y });
}
}
}
auto upgrade = [&](vector<string>& a, ll M) -> vector<string> {
auto b = a;
for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
if (dh[i][j] <= M) {
b[i][j] = 'H';
}
}
}
return b;
};
auto check = [&](vector<string>& a) -> bool {
queue<T> q;
vector<vector<ll>> d1(n, vector<ll>(n, MAX));
for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
if (a[i][j] == 'H') {
d1[i][j] = 0;
q.push({ i, j });
}
}
}
while (!q.empty()) {
T v = q.front();
q.pop();
for (ll i = 0; i < 4; ++i) {
ll x = v.x + dx[i], y = v.y + dy[i];
if (ok(x, y) && (a[x][y] == 'G' || a[x][y] == 'M') && d1[x][y] == MAX) {
d1[x][y] = d1[v.x][v.y] + 1;
q.push({ x, y });
}
}
}
vector<vector<ll>> d2(n, vector<ll>(n, MAX));
vector<vector<ll>> mod(n, vector<ll>(n, MAX));
q.push(s);
d2[s.x][s.y] = 0;
if (a[s.x][s.y] == 'H') {
return 0;
}
while (!q.empty()) {
T v = q.front();
q.pop();
for (ll i = 0; i < 4; ++i) {
ll x = v.x + dx[i], y = v.y + dy[i];
if (ok(x, y) && a[x][y] == 'G' && d2[x][y] == MAX) {
d2[x][y] = d2[v.x][v.y] + 1;
q.push({ x, y });
}
}
}
for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
if (d2[i][j] != MAX) {
mod[i][j] = d2[i][j] % k;
d2[i][j] = (d2[i][j] + k - 1) / k;
}
}
}
vector<vector<bool>> possible(n, vector<bool> (n));
for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
possible[i][j] = (a[i][j] == 'G' && (d2[i][j] < d1[i][j] || (d2[i][j] == d1[i][j] && mod[i][j] != 0)));
}
}
q.push(s);
vector<vector<ll>> vis(n, vector<ll> (n));
vis[s.x][s.y] = 1;
while (!q.empty()) {
T v = q.front();
q.pop();
for (ll i = 0; i < 4; ++i) {
ll x = v.x + dx[i], y = v.y + dy[i];
if (ok(x, y) && a[x][y] == 'G' && !vis[x][y] && possible[x][y]) {
vis[x][y] = 1;
q.push({ x, y });
}
}
}
ll ans = 0;
for (ll i = 0; i < 4; ++i) {
ll x = f.x + dx[i], y = f.y + dy[i];
if (ok(x, y) && vis[x][y] && (d2[x][y] < d1[x][y] || (d2[x][y] == d1[x][y] && mod[x][y] != 0))) {
ans |= 1;
}
}
/*for (ll i = 0; i < n; ++i) {
for (ll j = 0; j < n; ++j) {
cout << possible[i][j] << " \n"[j == n - 1];
}
}*/
return ans;
};
ll L = 0, R = 1e6;
while (R - L > 1) {
ll M = (L + R) / 2;
auto b = upgrade(a, M);
if (check(b)) {
L = M;
}
else {
R = M;
}
}
cout << (check(a) ? L : -1) << '\n';
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
/*cin >> t;*/
while (t--) {
solve();
}
return 0;
}
//4 1
//MGDG
//GGGG
//GGGG
//GGGH
