#include <bits/stdc++.h>
#define nmax 1002

using namespace std;
ifstream f("barbar.in");
ofstream g("barbar.out");
int n,m,dp[nmax][nmax];
int vect[4]={0,1,0,-1};
int vect2[4]={1,0,-1,0};
char mat[nmax][nmax];
bool marker[nmax][nmax],solutie;
pair <int ,int > x,y,dragon;
struct ceva
{
    bool operator()(pair<int ,int >a, pair<int ,int >b)
    {
        return dp[a.first][a.second]<dp[b.first][b.second];
    }
};
priority_queue <pair<int ,int >,vector <pair<int ,int > >,ceva> q;
void solve(int i,int j)
{
    q.push({i,j});
    while(!q.empty())
    {
        i=q.top().first;
        j=q.top().second;
        q.pop();

        if(i==y.first && j==y.second)
        {
            g<<dp[i][j];
            solutie=true;
            return ;
        }

        for(int d=0; d<4; d++)
        {
            int val=i+vect[d],val2=j+vect2[d];
            if(mat[val][val2]=='.')
            {
                dp[val][val2]=min(dp[val][val2],dp[i][j]);
                if(!marker[val][val2])
                {
                    q.push({val,val2});
                    marker[val][val2]=true;
                }
            }
        }
    }
}
int main()
{
    f>>n>>m;
    for(int i=1; i<=n; i++)
    {
        for(int j=1; j<=m; j++)
        {
            f>>mat[i][j];
            if(mat[i][j]=='D')dragon={i,j};
            else if(mat[i][j]=='I')
            {
                x={i,j};
                mat[i][j]='.';
            }
            else if(mat[i][j]=='O')
            {
                y={i,j};
                mat[i][j]='.';
            }
            dp[i][j]=nmax;
        }
    }
    queue < pair <int ,int > > q2;
    q2.push({dragon.first,dragon.second});
    dp[dragon.first][dragon.second]=0;
    while(!q2.empty())
    {
        int i=q2.front().first;
        int j=q2.front().second;
        q2.pop();
        marker[i][j]=false;
        for(int d=0; d<4; d++)
        {
            int val=i+vect[d],val2=j+vect2[d];
            if(mat[val][val2]=='D' && dp[val][val2]!=0)
            {
                dp[val][val2]=0;
                if(!marker[val][val2])
                {
                    q2.push({val,val2});
                    marker[val][val2]=true;
                }
            }
            else if(dp[i][j]+1<dp[val][val2] && mat[val][val2]=='.')
            {
                dp[val][val2]=dp[i][j]+1;
                if(!marker[val][val2])
                {
                    q2.push({val,val2});
                    marker[val][val2]=true;
                }
            }
        }
    }
    solve(x.first,x.second);
    if(!solutie)g<<-1;
    return 0;
}