#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif

using namespace std;
typedef long long ll;
typedef pair<int,int> Pint;
typedef pair<ll, ll> P;
//typedef pair<int, pair<int, int>> P;
//typedef tuple<int,int,int> T;
ll INFL = 1000000000000000010;//10^18 = 2^60
int INF = 2000000000;//10^9
ll MOD  = 1000000007;
//vector<int> dy = {0,0,1,-1};
//vector<int> dx = {1,-1,0,0};
#define MAX_V 1000010

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

vector<vector<edge>> G(MAX_V);
bool used[MAX_V];

void add_edge(int from, int to, int cap){
    edge F;
    edge T;
    F.to = to;
    F.cap = cap;
    F.rev = G[to].size();
    G[from].push_back(F);

    T.to = from;
    T.cap = 0;
    T.rev = G[from].size() - 1;
    G[to].push_back(T);
}

int dfs(int v, int t, int f){
    if(v == t) return f;
    used[v] = true;
    for(int i = 0; i < G[v].size(); i++){
        edge &e = G[v][i];
        if(!used[e.to] && e.cap > 0){
            int d = dfs(e.to, t, min(f, e.cap));
            if(d > 0){
                e.cap -= d;
                G[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}

int max_flow(int s, int t){
    int flow = 0;
    while(1){
        memset(used, 0, sizeof(used));
        int f = dfs(s, t, INF);
        if(f == 0) return flow;
        flow += f;
    }
}

int main(void){
  int H, W;
  cin >> H >> W;
  char mp[H][W];
  int sy, sx, gy, gx;
  for(int i = 0; i < H; i++){
    for(int j = 0; j < W; j++){
      cin >> mp[i][j];
      if(mp[i][j] == 'S') sy = i, sx = j;
      if(mp[i][j] == 'T') gy = i, gx = j;
    }
  }

  for(int i = 0; i < H; i++){
    for(int j = 0; j < W; j++){
      if(mp[i][j] == '.') continue;
      add_edge(i, j+100, 1);
      add_edge(j+100, i, 1);
    }
  }

  int s = 10000, g = 10001;
  add_edge(s, sy, INF);
  add_edge(s, sx+100, INF);
  add_edge(gy, g, INF);
  add_edge(gx+100, g, INF);

  if(sy == gy || sx == gx) cout << -1 << endl;
  else cout << max_flow(s, g) << endl;
}


Measured memory_bytes: 25344