#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <functional>
#include <set>
#include <ctime>
#include <random>
#include <chrono>
#include <cassert>
#include <tuple>
#include <utility>
using namespace std;

namespace {
  using Integer = long long; //__int128;
  template<class T, class S> istream& operator >> (istream& is, pair<T,S>& p){return is >> p.first >> p.second;}
  template<class T> istream& operator >> (istream& is, vector<T>& vec){for(T& val: vec) is >> val; return is;}
  template<class T> istream& operator ,  (istream& is, T& val){ return is >> val;}
  template<class T, class S> ostream& operator << (ostream& os, const pair<T,S>& p){return os << p.first << " " << p.second;}
  template<class T> ostream& operator << (ostream& os, const vector<T>& vec){for(size_t i=0; i<vec.size(); i++) os << vec[i] << (i==vec.size()-1?"":" "); return os;}
  template<class T> ostream& operator ,  (ostream& os, const T& val){ return os << " " << val;}

  template<class H> void print(const H& head){ cout << head; }
  template<class H, class ... T> void print(const H& head, const T& ... tail){ cout << head << " "; print(tail...); }
  template<class ... T> void println(const T& ... values){ print(values...); cout << endl; }

  template<class H> void eprint(const H& head){ cerr << head; }
  template<class H, class ... T> void eprint(const H& head, const T& ... tail){ cerr << head << " "; eprint(tail...); }
  template<class ... T> void eprintln(const T& ... values){ eprint(values...); cerr << endl; }

  class range{ Integer start_, end_, step_; public: struct range_iterator{ Integer val, step_; range_iterator(Integer v, Integer step) : val(v), step_(step) {} Integer operator * (){return val;} void operator ++ (){val += step_;} bool operator != (range_iterator& x){return step_ > 0 ? val < x.val : val > x.val;} }; range(Integer len) : start_(0), end_(len), step_(1) {} range(Integer start, Integer end) : start_(start), end_(end), step_(1) {} range(Integer start, Integer end, Integer step) : start_(start), end_(end), step_(step) {} range_iterator begin(){ return range_iterator(start_, step_); } range_iterator   end(){ return range_iterator(  end_, step_); } };

  inline string operator "" _s (const char* str, size_t size){ return move(string(str)); }
  constexpr Integer my_pow(Integer x, Integer k, Integer z=1){return k==0 ? z : k==1 ? z*x : (k&1) ? my_pow(x*x,k>>1,z*x) : my_pow(x*x,k>>1,z);}
  constexpr Integer my_pow_mod(Integer x, Integer k, Integer M, Integer z=1){return k==0 ? z%M : k==1 ? z*x%M : (k&1) ? my_pow_mod(x*x%M,k>>1,M,z*x%M) : my_pow_mod(x*x%M,k>>1,M,z);}
  constexpr unsigned long long operator "" _ten (unsigned long long value){ return my_pow(10,value); }

  inline int k_bit(Integer x, int k){return (x>>k)&1;} //0-indexed

  mt19937 mt(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count());

  template<class T> string join(const vector<T>& v, const string& sep){ stringstream ss; for(size_t i=0; i<v.size(); i++){ if(i>0) ss << sep; ss << v[i]; } return ss.str(); }

  inline string operator * (string s, int k){ string ret; while(k){ if(k&1) ret += s; s += s; k >>= 1; } return ret; }
}
constexpr long long mod = 9_ten + 7;


typedef struct{
  int to;
  int cap;
  int rev;
}edge;

// node v : distance from s => level[v]
void bfs(vector<vector<edge> > &G, vector<int> &level, int s){
  fill(level.begin(), level.end(), -1);
  queue<int> q;
  q.push(s);
  level[s] = 0;
  while(!q.empty()){
    int e=q.front(); q.pop();
    for(int i=0; i<G[e].size(); i++){
      if(G[e][i].cap > 0 && level[G[e][i].to] < 0){
        level[G[e][i].to] = level[e] + 1;
        q.push(G[e][i].to);
      }
    }
  }
}

int dfs(vector<vector<edge> > &G, vector<int> &level, vector<bool> &used, vector<int> &iter, int s, int f,  int t){
  if(s==t) return f;
  else{
    //iter[e] : done searching from v[0] to v[ iter[e]-1 ]
    for(int &i=iter[s]; i<G[s].size(); i++){
      //distance from s to v[e][i].to must be longer than dist from s to v
      if(G[s][i].cap > 0 && level[s] < level[ G[s][i].to ]){
        int d = dfs(G, level, used, iter, G[s][i].to, min(f, G[s][i].cap), t);
        if(d>0){
          G[s][i].cap -= d;
          G[ G[s][i].to ][ G[s][i].rev ].cap += d;
          return d;
        }
      }
    }
    return 0;
  }
}

int dinic_maxflow(vector<vector<edge> > &G, int s, int t){
  const int INF = 100000000;
  int flow=0;
  while(true){
    vector<int> level(G.size(), -1);
    vector<int> iter(G.size(), 0);
    vector<bool> used(G.size(), false);
    bfs(G, level, s);
    if(level[t] < 0) return flow; //unable to achieve to t
    while(true){
      int f = dfs(G, level, used, iter, s, INF, t);
      if(f==0) break;
      else flow += f;
    }
  }
}

void add_edge(vector<vector<edge> > &G, int from, int to, int cap){
  G[from].push_back((edge){to, cap, (int)G[to].size()});
  G[to].push_back((edge){from, 0, (int)G[from].size() - 1});
}

int main(){
  int h,w;
  cin >> h,w;
  vector<string> s(h);
  cin >> s;

  vector<vector<edge>> G(h*w*2 + h + w + 2);
  int source = h*w*2 + h + w + 0;
  int sink   = h*w*2 + h + w + 1;

  for(int i : range(h)){
    for(int j: range(w)){
      if( s[i][j] == '.') continue;
      if( s[i][j] == 'S'){
        add_edge(G, source, i*w + j, 1e6);
        add_edge(G, i*w+j, h*w + i*w+j, 1e6);
      }else if( s[i][j] == 'T'){
        add_edge(G, h*w + i*w + j, sink, 1e6);
        add_edge(G, i*w+j, h*w + i*w+j, 1e6);
      }else{
        add_edge(G, i*w+j, h*w + i*w+j, 1);
      }

      add_edge(G, h*w+i*w+j, h*w*2+i, 1e6);
      add_edge(G, h*w*2+i, i*w+j, 1e6);

      add_edge(G, h*w+i*w+j, h*w*2+h+j, 1e6);
      add_edge(G, h*w*2+h+j, i*w+j, 1e6);
    }
  }

  int f = dinic_maxflow(G, source, sink);

  if( f==1e6 ) f = -1;
  println(f);

  return 0;
}


Measured memory_bytes: 2868