#include<fstream>
#include<iomanip>
#include<queue>
#define nnn 1010
#define inf INT_MAX
using namespace std;
const int dx[]={0,0,-1,1};
const int dy[]={-1,1,0,0};
int m,n,sx,sy,fx,fy;
int d[nnn],a[nnn][nnn],v[nnn][nnn];
struct punct {int x,y;};
queue<punct> q;
punct p,o;
//  0 - liber
// -2 - dragon
//
ofstream out("barbar.out");
void afs()
{
	int i,j;
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++)
			out<<setfill(' ')<<setw(2)<<a[i][j]<<" ";
		out<<'\n';
	}	
	out<<"\n\n\n";
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++)
			out<<setfill(' ')<<setw(2)<<v[i][j]<<" ";
		out<<'\n';
	}
	out<<"\n\n\n";
	
			
}

void citire()
{
	int i,j;
	char c;
	ifstream in("barbar.in");
	in>>n>>m;
	in.get();	
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++)
		{
			in.get(c);
			if (c=='.')
				v[i][j]=0;
			else if (c=='D')
			{
				v[i][j]=-2;
				a[i][j]=-2;
				p.x=i;
				p.y=j;
				q.push(p);
			}
			else if (c=='*')
			{
				v[i][j]=-1;
				a[i][j]=-1;
			}
			else if (c=='I')
			{
				sx=i;
				sy=j;
			}
			else if (c=='O')
			{
				fx=i;
				fy=j;
			}
		}
		in.get();
	}
}


int val(int a)
{
	if (a==-2)
		return 0;
	return a;
}


void dist_dragoni()
{
	int x,y,i,xx,yy;
	while (!q.empty())
	{
		p=q.front();
		q.pop();
		x=p.x;
		y=p.y;
		for (i=0;i<4;i++)
		{
			xx=x+dx[i];
			yy=y+dy[i];
			if ( (!a[xx][yy]||a[xx][yy]>val(a[x][y])+1)&&xx>0&&yy>0&&xx<=n&&y<=m&&v[xx][yy]!=-1)
			{
				a[xx][yy]=val(a[x][y])+1;
				o.x=xx;
				o.y=yy;
				q.push(o);
			}
		}
	}
/*	for (i=1;i<=n;i++)
		for (j=1;j<=n;j++)
			if (v[i][j]==-2)
				v[i][j]=0;*/
}


void drum()
{
	int i,x,y,xx,yy;
	while (!q.empty())
		q.pop();
	p.x=sx;
	p.y=sy;
	q.push(p);
	v[sx][sy]=a[sx][sy];
	while (!q.empty())
	{
		p=q.front();
		q.pop();
		x=p.x;
		y=p.y;
		for (i=0;i<4;i++)
		{
			xx=x+dx[i];
			yy=y+dy[i];
			if (xx>0&&yy>0&&xx<=n&&y<=m&&v[xx][yy]!=-1)
			{
				if (!v[xx][yy])
				{
					v[xx][yy]=min(val(a[xx][yy]),val(v[x][y]));
					o.x=xx;
					o.y=yy;
					q.push(o);
				}
				else if (val(v[xx][yy])<val(a[xx][yy])&&val(v[x][y])>val(v[xx][yy]))
				{
					v[xx][yy]=min(v[x][y],a[xx][yy]);
					o.x=xx;
					o.y=yy;
					q.push(o);
				}
			}
		}
	}
}
			
		
	
int main()
{
	citire();
	dist_dragoni();	
	drum();
	
	//afs();
	if (v[fx][fy]==-2)
		out<<0<<'\n';
	else if (v[fx][fy]==0)
		out<<-1;
	else
		out<<val(v[fx][fy])<<'\n';
}