#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

#define REP(i,s,n) for(int i=(int)(s);i<(int)(n);i++)

using namespace std;
typedef long long int ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef pair<int, int> PI;

/**
 * Dinic's algorithm for maximum flow problem.
 * Header requirement: vector, queue
 * Verified by: ABC010-D(http://abc010.contest.atcoder.jp/submissions/602810)
 *              ARC031-D(http://arc031.contest.atcoder.jp/submissions/1050071)
 *              POJ 3155(http://poj.org/problem?id=3155)
 */
template<class T = int>
class Dinic {
private:
  struct edge {
    int to;
    T cap;
    int rev; // rev is the position of reverse edge in graph[to]
  };
  std::vector<std::vector<edge> > graph;
  std::vector<int> level;
  std::vector<int> iter;
  /* Perform bfs and calculate distance from s */
  void bfs(int s) {
    level.assign(level.size(), -1);
    std::queue<int> que;
    level[s] = 0;
    que.push(s);
    while (! que.empty()) {
      int v = que.front(); que.pop();
      for (int i = 0; i < graph[v].size(); ++i) {
	edge &e = graph[v][i];
	if (e.cap > 0 && level[e.to] == -1) {
	  level[e.to] = level[v] + 1;
	  que.push(e.to);
	}
      }
    }
  }
  /* search augment path by dfs.
     if f == -1, f is treated as infinity. */
  T dfs(int v, int t, T f) {
    if (v == t) {
      return f;
    }
    for (int &i = iter[v]; i < (int) graph[v].size(); ++i) {
      edge &e = graph[v][i];
      if (e.cap > 0 && level[v] < level[e.to]) {
	T newf = f == -1 ? e.cap : std::min(f, e.cap);
	T d = dfs(e.to, t, newf);
	if (d > 0) {
	  e.cap -= d;
	  graph[e.to][e.rev].cap += d;
	  return d;
	}
      }
    }
    return 0;
  }
public:
  /* v is the number of vertices (labeled from 0 .. v-1) */
  Dinic(int v) : graph(v), level(v, -1), iter(v, 0) {}
  void add_edge(int from, int to, T cap) {
    graph[from].push_back((edge) {to, cap, graph[to].size()});
    graph[to].push_back((edge) {from, 0, graph[from].size() - 1});
  }
  T max_flow(int s, int t) {
    T flow = 0;
    while (1) {
      bfs(s);
      if (level[t] < 0) {
	return flow;
      }
      iter.assign(iter.size(), 0);
      T f;
      while ((f = dfs(s, t, -1)) > 0) {
	flow += f;
      }
    }
  }
  std::pair<T,std::vector<int> > max_flow_cut(int s, int t) {
    T flow = 0;
    while (1) {
      bfs(s);
      if (level[t] < 0) {
	std::vector<int> ret;
	for (int i = 0; i < graph.size(); ++i) {
	  if (level[i] < 0) {
	    ret.push_back(i);
	  }
	}
	return std::pair<T, std::vector<int> >(flow, ret);
      }
      iter.assign(iter.size(), 0);
      T f;
      while ((f = dfs(s, t, -1)) > 0) {
	flow += f;
      }
    }
  }
};

const ll inf = 1e15;

const int N = 114;
string a[N];

int main(void){
  int h, w;
  cin >> h >> w;
  PI s(-1, -1), t(-1, -1);
  REP(i, 0, h) {
    cin >> a[i];
    REP(j, 0, w) {
      char c = a[i][j];
      if (c == 'S') {
	s = PI(i, j);
      }
      if (c == 'T') {
	t = PI(i, j);
      }
    }
  }
  if (s.first == t.first || s.second == t.second) {
    cout << -1 << endl;
    return 0;
  }
  // Objective is possible.
  Dinic<ll> din(2 * h * w + h + w);
  int s_id = s.first * w + s.second;
  int t_id = t.first * w + t.second;
  REP(i, 0, h) {
    REP(j, 0, w) {
      int v = i * w + j;
      if (a[i][j] != '.') {
	din.add_edge(2 * v, 2 * v + 1, 1);
      }
    }
  }
  REP(i, 0, h) {
    int aux = 2 * h * w + i;
    REP(j, 0, w) {
      int v = i * w + j;
      din.add_edge(aux, 2 * v, inf);
      din.add_edge(2 * v + 1, aux, inf);
    }
  }
  REP(j, 0, w) {
    int aux = 2 * h * w + h + j;
    REP(i, 0, h) {
      int v = i * w + j;
      din.add_edge(aux, 2 * v, inf);
      din.add_edge(2 * v + 1, aux, inf);
    }
  }
  cout << din.max_flow(2 * s_id + 1, 2 * t_id) << endl;
}


Measured memory_bytes: 4480