#include <bits/stdc++.h>
using namespace std;
class input {
private:
FILE* fin;
const int sz = 10000;
char* buff, c;
int p;
const char stop = char(-51);
char read()
{
if (p == sz)
{
fread(buff, 1, sz, fin);
p = 0;
return buff[p++];
}
else
return buff[p++];
}
bool digit(char c)
{
return c >= '0' && c <= '9';
}
public:
input(const char* name)
{
c = '-';
buff = new char[sz];
p = 0;
fin = fopen(name, "r");
fread(buff, 1, sz, fin);
}
void close()
{
fclose(fin);
}
void open(const char* name)
{
c = '-';
p = sz;
fin = fopen(name, "r");
}
bool eof()
{
int i = p;
while (true)
{
while (i < sz && (buff[i] == ' ' || buff[i] == '\n'))
i++;
if (i != sz)
{
if (buff[i] == stop)
return 1;
return 0;
}
else
{
fread(buff, 1, sz, fin);
p = 0;
i = 0;
}
}
}
input& operator >> (int& n)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
n = 0;
int sng = 1;
if (c == '-')
sng = -1, c = read();
while (digit(c))
n = n * 10 + (c - '0'), c = read();
n *= sng;
return *this;
}
input& operator >> (long long& n)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
n = 0;
int sng = 1;
if (c == '-')
sng = -1, c = read();
while (digit(c))
n = n * 10 + (c - '0'), c = read();
n *= sng;
return *this;
}
input& operator >> (unsigned long long& n)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
n = 0;
int sng = 1;
if (c == '-')
sng = -1, c = read();
while (digit(c))
n = n * 10 + (c - '0'), c = read();
n *= sng;
return *this;
}
input& operator >> (char& ch)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
ch = c;
return *this;
}
input& operator >> (string& n)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
n = "";
while (c != ' ' && c != '\n' && c != '\0')
n += c, c = read();
return *this;
}
input& operator >> (double& n)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
n = 0;
while (digit(c))
n = n * 10 + (c - '0'), c = read();
if (c != '.')
return *this;
c = read();
double p10 = 10;
while (digit(c))
n = n + double(c - '0') / p10, c = read(), p10 *= 10;
return *this;
}
input& operator >> (char* s)
{
c = read();
while (c == ' ' || c == '\n')
c = read();
while (c != ' ' && c != '\n')
*s = c, s++, c = read();
*s = '\0';
return *this;
}
void getline(string& s)
{
s = "";
c = read();
while (c == ' ')
c = read();
while (c != '\n')
s += c, c = read();
}
};
class output {
private:
FILE* fout;
const int sz = 10000;
char* buff;
int p;
void write(char ch)
{
if (p == sz)
{
fwrite(buff, 1, sz, fout);
p = 0;
buff[p++] = ch;
}
else
buff[p++] = ch;
}
public:
output(const char* name)
{
buff = new char[sz];
p = 0;
fout = fopen(name, "w");
}
~output()
{
fwrite(buff, 1, p, fout);
}
output& operator << (int n)
{
if (n < 0)
write('-'), n *= -1;
if (n == 0)
{
write(n + '0');
return *this;
}
if (n / 10 != 0)
*this << (n / 10);
write(('0' + (n % 10)));
return *this;
}
output& operator << (long long n)
{
if (n < 0)
{
write('-');
n *= -1;
}
if (n < 10)
{
write(n + '0');
return *this;
}
*this << (n / 10);
write((n % 10) + '0');
return *this;
}
output& operator << (unsigned long long n)
{
if (n < 0)
{
write('-');
n *= -1;
}
if (n < 10)
{
write(n + '0');
return *this;
}
*this << (n / 10);
write((n % 10) + '0');
return *this;
}
output& operator << (char c)
{
write(c);
return *this;
}
void precision(double n, int x)
{
*this << int(n);
if (!x)
return;
write('.');
n -= int(n);
n *= 10;
for (int i = 1; i <= x; i++)
{
*this << int(n);
n -= int(n);
n *= 10;
}
}
output& operator << (string n)
{
for (auto i : n)
write(i);
return *this;
}
};
ifstream fin("barbar.in");
ofstream fout("barbar.out");
int n, m, minDst[1001][1001];
char a[1001][1001];
pair <int, int> Begin, End;
bitset <1001> f[1001];
int d1[] = { 0, -1, 0, 1, 0 };
int d2[] = { 0, 0, 1, 0, -1 };
struct nod {
int i, j;
bool operator < (const nod& aux) const
{
return minDst[i][j] > minDst[aux.i][aux.j];
}
};
inline bool in(int i, int j)
{
return i >= 1 && i <= n && j >= 1 && j <= m;
}
bool lee(int val)
{
for (int i = 1; i <= 1000; i++)
f[i].reset();
queue <pair<int, int>> Q;
Q.push(Begin);
f[Begin.first][Begin.second] = 1;
while (!Q.empty())
{
int i = Q.front().first;
int j = Q.front().second;
Q.pop();
if (End == make_pair(i, j))
return true;
for (int k = 1; k <= 4; k++)
{
int x = i + d1[k];
int y = j + d2[k];
if (in(x, y) && a[x][y] != '*' && minDst[x][y] >= val && !f[x][y])
{
f[x][y] = 1;
Q.push({ x, y });
}
}
}
return false;
}
int main()
{
fin >> n >> m;
priority_queue <nod> Q;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
{
fin >> a[i][j];
if (a[i][j] == 'I')
Begin = { i, j }, minDst[i][j] = INT_MAX;
else if (a[i][j] == 'O')
End = { i, j }, minDst[i][j] = INT_MAX;
else if (a[i][j] == 'D')
minDst[i][j] = 0, Q.push({ i, j });
else
minDst[i][j] = INT_MAX;
}
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
fin >> a[i][j];
while (!Q.empty())
{
int i = Q.top().i;
int j = Q.top().j;
Q.pop();
for (int k = 1; k <= 4; k++)
{
int x = i + d1[k];
int y = j + d2[k];
if (in(x, y) && a[x][y] != '*' && minDst[x][y] > minDst[i][j] + 1)
{
minDst[x][y] = minDst[i][j] + 1;
Q.push({ x, y });
}
}
}
int l = 1, r = min(minDst[Begin.first][Begin.second], minDst[End.first][End.second]), poz = -1;
while (l <= r)
{
int m = (l + r) / 2;
if (lee(m))
{
poz = m;
l = m + 1;
}
else
r = m - 1;
}
fout << poz;
return 0;
}