#include<cstdio>
#include<queue>
using namespace std;

#define nrn 1024

struct punct{int x,y;}s,f,p;
queue<punct>Q;
const int dx[]={0,-1,0,1,0};
const int dy[]={0,0,1,0,-1};
int a[nrn][nrn],m[nrn][nrn];

void citire()
{
    int i,j,L,C;
    char x;
    FILE *in=fopen("barbar.in","r");
    fscanf(in,"%d %d\n",&L,&C);
    for(i=1;i<=L;++i)
    {
        for(j=1;j<=C;++j)
        {
            fscanf(in,"%c",&x);
            switch(x)
            {
                case('*'):
                a[i][j]=-1;
                m[i][j]=-1;
                break;

                case('D'):
                //a[i][j]=-2;
                m[i][j]=-2;
                p.x=i;
                p.y=j;
                Q.push(p);
                break;

                case('I'):
                s.x=i;
                s.y=j;
                break;

                case('O'):
                f.x=i;
                f.y=j;
                break;
            }
        }
        fscanf(in,"\n");
    }
    fclose(in);
    for(i=0;i<=L+1;++i)
        a[i][0]=a[i][C+1]=m[i][0]=m[i][C+1]=-1;
    for(j=1;j<=C;++j)
        a[0][j]=a[L+1][j]=m[0][j]=m[L+1][j]=-1;
}

void drum()
{
    int x,y,xx,yy,i;
    while(!Q.empty())
    {
        p=Q.front();
        Q.pop();
        x=p.x;
        y=p.y;
        for(i=1;i<5;++i)
        {
            xx=x+dx[i];
            yy=y+dy[i];
            if((!a[xx][yy] || a[xx][yy]>a[x][y]+1) && m[xx][yy]>-1)
            {
                a[xx][yy]=a[x][y]+1;
                p.x=xx;
                p.y=yy;
                Q.push(p);
            }
        }
    }
    m[s.x][s.y]=a[s.x][s.y];
    Q.push(s);
    while(!Q.empty())
    {
        p=Q.front();
        Q.pop();
        x=p.x;
        y=p.y;
        for(i=1;i<5;++i)
        {
            xx=x+dx[i];
            yy=y+dy[i];
            if(m[xx][yy]!=-1)
            {
               // if(m[xx][yy]==-2)
               //     m[xx][yy]=0;
                if(!m[xx][yy] || (m[xx][yy]<m[x][y] && m[xx][yy]<a[xx][yy]))
                {
                    m[xx][yy]=min(a[xx][yy],m[x][y]);
                    p.x=xx;
                    p.y=yy;
                    Q.push(p);
                }
            }
        }
    }
}

void afisare()
{
    int x,y;
    FILE *out=fopen("barbar.out","w");
    x=f.x;
    y=f.y;
    if(!m[x][y])
        fprintf(out,"-1\n");
    else fprintf(out,"%d\n",m[x][y]);
    fclose(out);
}

int main()
{
    citire();
    drum();
    afisare();
    return 0;
}