#include <fstream.h>

#define min(a, b) (a < b ? a : b)

int R, C, i, j, l[2] = {-1, -1}, o = 0, v[2][2][1050000], m[1050][1050], iesirex, iesirey, m2[1050][1050];
int pozbarx, pozbary, block = 0, nr2 = 1, a, b, chestie, avx;
char cit[1500], dummy[7];

void citire ()
{
	memset (m, -1, sizeof (m));
	memset (m2, -1, sizeof (m2));
	ifstream fin ("barbar.in");
	fin >> R >> C;
	fin.getline (dummy, 5);
	for (i = 0; i < R; i++)
	{
		fin.getline (cit, 1050);
		for (j = 0; j < C; j++)
		{
			if (cit[j] != '.')
			{
				if (cit[j] == 'D')
				{
					m[i][j] = - 3;
					m2[i][j] = 0;
					v[0][0][++l[0]] = i;
					v[0][1][l[0]] = j;
				}
				else
				{
					if (cit[j] == '*')
					{
						m[i][j] = -2;
						m2[i][j] = -2;
					}
					else
					{
						if (cit[j] == 'I')
						{
							pozbarx = i;
							pozbary = j;
						}
						else
						{
							iesirex = i;
							iesirey = j;
						}
					}
				}
			}
		}
	}
	fin.close ();
}

void ChangeD (int x, int y, int avx)
{
	if (x == -1 || x == R || y == -1 || y == C || m2[x][y] != -1) return;
	m2[x][y] = nr2;
	v[avx][0][++l[avx]] = x;
	v[avx][1][l[avx]] = y;
	block = 0;
}

/*void Scriere ()
{
	for (i = 0; i < R; i++)
	{
		for (j = 0; j < C; j++)
		{
			cout << m[i][j] << " ";
		}
		cout << "\n";
	}
	cout << "\n\n\n";
}*/

void DStep (int &o)
{
	avx = (o + 1) & 1;
	l[avx] = -1;
	block = 1;
	for (i = 0; i <= l[o]; i++)
	{
		a = v[o][0][i];
		b = v[o][1][i];
		ChangeD (a + 1, b, avx);
		ChangeD (a - 1, b, avx);
		ChangeD (a, b + 1, avx);
		ChangeD (a, b - 1, avx);
	}
	o = avx;
	nr2++;
}

void diverse ()
{
	l[0] = 0;
	v[0][0][0] = pozbarx;
	v[0][1][0] = pozbary;
	m[pozbarx][pozbary] = m2[pozbarx][pozbary];
	block = 0;
	o = 0;
}

void ChangeBar (int x, int y, int avx, int xvechi, int yvechi)
{
	if (x == -1 || x == R || y == -1 || y == C || m[x][y] == -2) return;
	chestie = min (m2[x][y], m[xvechi][yvechi]);
	if (m[x][y] < chestie)
	{
		block = 0;
		m[x][y] = chestie;
		v[avx][0][++l[avx]] = x;
		v[avx][1][l[avx]] = y;
	}
}

void BStep (int &o)
{
	avx = (o + 1) & 1;
	l[avx] = -1;
	block = 1;
	for (i = 0; i <= l[o]; i++)
	{
		a = v[o][0][i];
		b = v[o][1][i];
		ChangeBar (a - 1, b, avx, a, b);
		ChangeBar (a + 1, b, avx, a, b);
		ChangeBar (a, b - 1, avx, a, b);
		ChangeBar (a, b + 1, avx, a, b);
	}
	o = avx;
}

void scriere ()
{
	ofstream fout ("barbar.out");
	fout << m[iesirex][iesirey];
	fout.close ();
}

int main ()
{
	citire ();
	while (!block) DStep (o);
	diverse ();
	while (!block) BStep (o);
	scriere ();
	return 0;
}