//grok debug
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
const int mxN = 8e2;
char c[mxN][mxN];
int vis[mxN][mxN]; // Time bees reach each cell
bool vis1[mxN][mxN]; // Visited in Mecho's BFS
pair<int, int> st, ed;
int n, s;
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
// Bees spread to grassy cells only (G, M)
bool bee_valid(int x, int y) {
return (x >= 0 && x < n && y >= 0 && y < n && (c[x][y] == 'G' || c[x][y] == 'M'));
}
// Mecho moves to grass (G, M) and home (D)
bool mecho_valid(int x, int y) {
return (x >= 0 && x < n && y >= 0 && y < n &&
(c[x][y] == 'G' || c[x][y] == 'M' || c[x][y] == 'D'));
}
bool check(int x) {
// Check if Mecho is safe at M for x minutes
if (vis[st.ff][st.ss] <= x) return 0;
queue<array<int, 4>> q; // {x, y, step, state}
q.push({st.ff, st.ss, x + 1, 0});
memset(vis1, 0, sizeof(vis1));
vis1[st.ff][st.ss] = 1;
while (!q.empty()) {
auto [xx, yy, step, state] = q.front();
q.pop();
if (xx == ed.ff && yy == ed.ss) return 1;
for (int i = 0; i < 4; i++) {
int nx = xx + dx[i], ny = yy + dy[i];
if (mecho_valid(nx, ny) && vis[nx][ny] > step && !vis1[nx][ny]) {
vis1[nx][ny] = 1;
int new_state = state + 1;
if (new_state == s) {
q.push({nx, ny, step + 1, 0});
} else {
q.push({nx, ny, step, new_state});
}
}
}
}
return 0;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> s;
// Compute bee spread times
queue<array<int, 3>> q;
memset(vis, 0x3f, sizeof(vis));
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
cin >> c[i][j];
if (c[i][j] == 'M') st = {i, j};
if (c[i][j] == 'D') ed = {i, j};
if (c[i][j] == 'H') q.push({i, j, 0}), vis[i][j] = 0;
}
}
while (!q.empty()) {
auto [x, y, now] = q.front();
q.pop();
for (int i = 0; i < 4; i++) {
int nx = x + dx[i], ny = y + dy[i];
if (vis[nx][ny] == 0x3f3f3f3f && bee_valid(nx, ny)) {
vis[nx][ny] = now + 1;
q.push({nx, ny, now + 1});
}
}
}
// Binary search for maximum k
int l = 0, r = n, ans = -1; // r=n is safer than r=s
while (l <= r) {
int mid = (l + r) / 2;
if (check(mid)) {
ans = mid;
l = mid + 1;
} else {
r = mid - 1;
}
}
cout << ans << "\n";
return 0;
}
