#include <fstream>
#include <queue>
using namespace std;
ifstream f("barbar.in");
ofstream g("barbar.out");
#define oo (1 << 30)
const int NMAX = 1005;
int n, m, b[NMAX][NMAX], c[NMAX][NMAX];
int dx[] = { 1,-1,0,0 };
int dy[] = { 0,0,1,-1 };
char a[NMAX][NMAX];
int OK(int i, int j)
{
	if (i<1 || i>n || j<1 || j>m)
		return 0;
	if (a[i][j] != '*')
		return 1;
	return 0;
}

int main()
{
	int x1, x2, y1, y2;
	queue< pair <int, int> > coada;
	f >> n >> m;
	for(int i=1;i<=n;i++)
		for (int j = 1; j <= m; j++)
		{
			f >> a[i][j];
			if (a[i][j] == 'D')
			{
				coada.push(make_pair(i, j));
				b[i][j] = 0;
			}
			else
			{
				if (a[i][j] == 'I')
				{
					x1 = i;
					y1 = j;
				}
				else
					if (a[i][j] == 'O')
					{
						x2 = i;
						y2 = j;
					}
				b[i][j] = oo;
			}
		}
	while (!coada.empty())
	{
		int x = coada.front().first;
		int y = coada.front().second;
		coada.pop();
		for (int directie = 0; directie < 4; directie++)
		{
			int x_urmator = x + dx[directie];
			int y_urmator = y + dy[directie];
			if (OK(x_urmator, y_urmator) && b[x_urmator][y_urmator] > b[x][y] + 1)
			{
				b[x_urmator][y_urmator] = 1 + b[x][y];
				coada.push(make_pair(x_urmator, y_urmator));
			}
		}
	}
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			c[i][j] = -1;
	coada.push(make_pair(x1, y1));
	c[x1][y1] = b[x1][y1];
	while (!coada.empty())
	{
		int x = coada.front().first;
		int y = coada.front().second;
		coada.pop();
		for (int directie = 0; directie < 4; directie++)
		{
			int x_urmator = x + dx[directie];
			int y_urmator = y + dy[directie];
			if (OK(x_urmator, y_urmator))
			{
				if (c[x_urmator][y_urmator] == -1)
				{
					c[x_urmator][y_urmator] = min(b[x_urmator][y_urmator], c[x][y]);
					coada.push(make_pair(x_urmator, y_urmator));
				}
				else
					if (c[x_urmator][y_urmator] < min(c[x][y], b[x_urmator][y_urmator]))
					{
						c[x_urmator][y_urmator] = min(c[x][y], b[x_urmator][y_urmator]);
						coada.push(make_pair(x_urmator, y_urmator));
					}
			}
		}
	}
	g << c[x2][y2];
}