#include <bits/stdc++.h>
using namespace std;
#define inputJunk ios_base::sync_with_stdio(0); cin.tie(0);
#define pb push_back
#define f first
#define s second
#define all(x) x.begin(), x.end()
#define debug cout<<"HERE"<<endl;
#define ell "\n"
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;
typedef pair<pi, int> trip;
typedef pair<pll, ll> tripll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pi> vpi;
typedef vector<pll> vpll;
typedef vector<trip> vtrip;
const int INF = 1e9+1212;
const ll P = 9973, M = 1e9+9;
const int MM = 8e2+5; int mod = 1e9+7;//998244353
int n, k, sx, sy, ex, ey, dist[MM][MM]; char grid[MM][MM];
queue<pi> q; pi dir[4] {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
pi step[MM][MM];
bool vv(int a){
return a>=0&&a<n;
}
bool valid(int x, int y){
return vv(x)&&vv(y)&&(grid[x][y]=='G'||grid[x][y]=='M')&dist[x][y]==-1;
}
bool dfs(int t){
queue<pi> q;
for(int i = 0;i<n;i++){
for(int j = 0;j<n;j++){
step[i][j] = {-1, 0};
}
}
step[sx][sy] = {t, 0};
q.push({sx, sy});
while(!q.empty()){
int x = q.front().f, y = q.front().s; q.pop();
for(int i = 0;i<4;i++){
int newx = x+dir[i].f, newy = y+dir[i].s;
//cout<<newx<<" "<<newy<<endl;
if(vv(newx)&&vv(newy)&&(grid[newx][newy]=='G'||grid[newx][newy]=='D')&&step[x][y].f<dist[newx][newy]&&step[newx][newy].f==-1){
int newt = (step[x][y].s+1==k)?step[x][y].f+1:step[x][y].f;
int newused = (step[x][y].s+1)%k;
step[newx][newy] = {newt, newused};
q.push({newx, newy});
}
}
}
return step[ex][ey].f!=-1;
}
int main(){
inputJunk
cin>>n>>k;
for(int i = 0;i<n;i++){
for(int j = 0;j<n;j++){
cin>>grid[i][j];
dist[i][j] = -1;
if(grid[i][j]=='M'){sx = i; sy = j;}
else if(grid[i][j]=='D'){ex = i;ey = j;}
else if(grid[i][j]=='H'){q.push({i, j}); dist[i][j] = 0;}
}
}
while(!q.empty()){
int curx = q.front().f, cury = q.front().s;q.pop();
//cout<<curx<<" "<<cury<<" "<<endl;
for(int i = 0;i<4;i++){
int newx = curx+dir[i].f, newy = cury+dir[i].s;
if(valid(newx, newy)){
dist[newx][newy] = dist[curx][cury]+1;
q.push({newx, newy});
}
}
}
/*
for(int i = 0;i<n;i++){
for(int j = 0;j<n;j++){
cout<<dist[i][j]<<" ";
}cout<<ell;
}*/
dist[ex][ey] = INF;
int lo = 0, hi = 100000;
if(!dfs(0)){
cout<<-1<<endl;
return 0;
}
//cout<<"BOB"<<dfss(2)<<ell;
while(lo<hi){
//cout<<lo<<" "<<hi<<endl;
int mid = (lo+hi+1)/2;
if(dfs(mid)){
lo = mid;
}else{
hi = mid-1;
}
}
cout<<lo<<endl;
}
/*CUSTOM TEST CASE 1
*/
/*CUSTOM TEST CASE 2
*/
/*CUSTOM TEST CASE 3
*/
/*Comments of Shame
- floating error (use integer division instead)
- cin vs getline
- upperbound and lowerbound returns iteratorsf
- use long long when number is big enough
- for dp invalid cases needs to be skipped
- some base cases won't work (review cow poetry)
- always check bounds, some TLE are due to incorrect bounds!
- dont mess up return types
= RESET ARRAYS!!!!!!!!!!
- USE UR BRAIN
- INF setting problems
*/
/*
freopen("time.in","r", stdin);
freopen("time.out","w", stdout);
*/
