#include <bits/stdc++.h>
#define FOR(v, a, b) for(int v = (a); v < (b); ++v)
#define FORE(v, a, b) for(int v = (a); v <= (b); ++v)
#define REP(v, n) FOR(v, 0, n)
#define REPE(v, n) FORE(v, 0, n)
#define REV(v, a, b) for(int v = (a); v >= (b); --v)
#define ALL(x) (x).begin(), (x).end()
#define ITR(it, c) for(auto it = (c).begin(); it != (c).end(); ++it)
#define RITR(it, c) for(auto it = (c).rbegin(); it != (c).rend(); ++it)
#define EXIST(c,x) ((c).find(x) != (c).end())
#define LLI long long int
#define fst first
#define snd second

#ifdef DEBUG
#include <misc/C++/Debug.cpp>
#else
#define dump(x)
#endif

#define gcd __gcd

using namespace std;
template <class T> constexpr T lcm(T m, T n){return m/gcd(m,n)*n;}

template <typename I> void join(ostream &ost, I s, I t, string d=" "){for(auto i=s; i!=t; ++i){if(i!=s)ost<<d; ost<<*i;}ost<<endl;}
template <typename T> istream& operator>>(istream &is, vector<T> &v){for(auto &a : v) is >> a; return is;}
template <typename T, typename U> istream& operator>>(istream &is, pair<T,U> &p){is >> p.first >> p.second; return is;}

template <typename T, typename U> T& chmin(T &a, const U &b){return a = (a<=b?a:b);}
template <typename T, typename U> T& chmax(T &a, const U &b){return a = (a>=b?a:b);}
template <typename T, size_t N, typename U> void fill_array(T (&a)[N], const U &v){fill((U*)a, (U*)(a+N), v);}

template <typename T, T INF> class FordFulkerson{ 
public:
  struct edge{
    int to, rev;
    T cap;
  };

  int size;

  vector<vector<edge>> graph;
  vector<bool> visit;
  
  FordFulkerson(int size): size(size), graph(size), visit(size){}

  void add_edge(int from, int to, const T &cap){
    graph[from].push_back((edge){to, (int)graph[to].size(), cap});
    graph[to].push_back((edge){from, (int)graph[from].size()-1, 0});
  }

  T dfs(int from, int to, T flow){
    if(from == to) return flow;
    visit[from] = true;

    for(auto &e : graph[from]){
      if(!visit[e.to] and e.cap > 0){
	int d = dfs(e.to, to, min(flow, e.cap));
	if(d > 0){
	  e.cap -= d;
	  graph[e.to][e.rev].cap += d;
	  return d;
	}
      }
    }
    return 0;
  }
  
  T max_flow(int s, int t){
    T ret = 0;

    while(1){
      visit.assign(size,false);
      T flow = dfs(s,t,INF);
      if(flow == 0) return ret;
      ret += flow;
    }
  }
};


const int inf = INT_MAX/2;

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int H,W;
  while(cin >> H >> W){
    vector<string> S(H); cin >> S;
    vector<vector<int>> field(H, vector<int>(W,-1));

    int s,t;
    int c = 0;
    {
      REP(i,H){
	REP(j,W){
	  if(S[i][j] == 'S') s = c;
	  if(S[i][j] == 'T') t = c;
	  
	  if(S[i][j] != '.'){
	    field[i][j] = c;
	    ++c;
	  }
	}
      }
    }

    FordFulkerson<int,inf> mf(c*2);
    
    vector<int> out(c), in(c);
    REP(i,c){
      in[i] = i;
      out[i] = c+i;
      if(i == s or i == t) mf.add_edge(in[i],out[i],inf);
      else mf.add_edge(in[i],out[i],1);
    }
    
    REP(i,H){
      REP(j,W){
	if(field[i][j] == -1) continue;
	REP(k,H){
	  if(field[k][j] != -1 and i != k) mf.add_edge(out[field[i][j]], in[field[k][j]], inf);
	}

	REP(k,W){
	  if(field[i][k] != -1 and j != k) mf.add_edge(out[field[i][j]], in[field[i][k]], inf);
	}
      }
    }
    
    int ans = mf.max_flow(out[s], in[t]);
    cout << (ans>=inf ? -1 : ans) << endl;
  }
  
  return 0;
}


Measured memory_bytes: 63104