#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define mp make_pair
#define pb push_back
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)

template< typename flow_t >
struct Dinic {
  const flow_t INF;

  struct edge {
    int to;
    flow_t cap;
    int rev;
    bool isrev;
    int idx;
  };

  vector< vector< edge > > graph;
  vector< int > min_cost, iter;

  Dinic(int V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

  void add_edge(int from, int to, flow_t cap, int idx = -1) {
    graph[from].emplace_back((edge) {to, cap, (int) graph[to].size(), false, idx});
    graph[to].emplace_back((edge) {from, 0, (int) graph[from].size() - 1, true, idx});
  }

  bool bfs(int s, int t) {
    min_cost.assign(graph.size(), -1);
    queue< int > que;
    min_cost[s] = 0;
    que.push(s);
    while(!que.empty() && min_cost[t] == -1) {
      int p = que.front();
      que.pop();
      for(auto &e : graph[p]) {
        if(e.cap > 0 && min_cost[e.to] == -1) {
          min_cost[e.to] = min_cost[p] + 1;
          que.push(e.to);
        }
      }
    }
    return min_cost[t] != -1;
  }

  flow_t dfs(int idx, const int t, flow_t flow) {
    if(idx == t) return flow;
    for(int &i = iter[idx]; i < graph[idx].size(); i++) {
      edge &e = graph[idx][i];
      if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
        flow_t d = dfs(e.to, t, min(flow, e.cap));
        if(d > 0) {
          e.cap -= d;
          graph[e.to][e.rev].cap += d;
          return d;
        }
      }
    }
    return 0;
  }

  flow_t max_flow(int s, int t) {
    flow_t flow = 0;
    while(bfs(s, t)) {
      iter.assign(graph.size(), 0);
      flow_t f = 0;
      while((f = dfs(s, t, INF)) > 0) flow += f;
    }
    return flow;
  }

  void output() {
    for(int i = 0; i < graph.size(); i++) {
      for(auto &e : graph[i]) {
        if(e.isrev) continue;
        auto &rev_e = graph[e.to][e.rev];
        cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
      }
    }
  }
};

// vector<int> g[1000];

// bool dfs(int gx, int gy, int cv, int pv, set<int> &used_v, vector<int> &reach_v){
//   if(used_v.count(cv)) return reach_v[cv];
//   bool reach = false;
//   for(auto i:g[cv]){
//     // cout << "cv nv pv used " << cv << " " << i  << " " << pv  << " " << used_v.count(i)<< endl;
//     if(i==pv) continue;
//     if(used_v.count(i)) {
//       reach = reach || reach_v[i];
//       continue;
//     }
//     bool res = dfs(gx,gy,i,cv,used_v,reach_v);
//     reach = reach || res;
//   }
//   reach_v[cv] = reach;
//   used_v.insert(i);
//   return reach_v[cv];
// }

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

  int h,w;
  cin >> h >> w;
  vector<string> a(h);
  rep(i,h) cin >> a[i];
  int sx,sy,gx,gy;

  rep(i,h)rep(j,w){
    int xi = j;
    int yi = 500 +i;
    // if(a[i][j]!='.'){
    //   g[xi].pb(yi);
    //   g[yi].pb(xi);
    // }
    if(a[i][j]=='S'){
      sx = xi;
      sy = yi;
    }
    else if(a[i][j]=='T'){
      gx = xi;
      gy = yi;
    }
  }
  if(sx == gx || sy == gy){
    cout << -1 << endl;
    return 0;
  }
  // set<int> use_v;
  // vector<int> reach_v(2000,false);
  // reach_v[gx] = reach_v[gy] = true;

  // dfs(gx,gy,sx,-1,use_v,reach_v);
  // dfs(gx,gy,sy,-1,use_v,reach_v);

  // int vertex = 0;
  // map<int,int> vmap;
  // rep(i,2000) {
  //   if(reach_v[i]) {
  //     vmap[i] = vertex++;
  //     // cout << i << " " << vertex << endl;
  //   }
  // }  


  Dinic<int> gr(1000+2);
  rep(i,h)rep(j,w){
    int xi = j;
    int yi = 500 +i;
    if(a[i][j] == 'o'){
      gr.add_edge(xi,yi,1);
      gr.add_edge(yi,xi,1);
      // gr.add_edge(vmap[xi],vmap[yi],1);
      // gr.add_edge(vmap[yi],vmap[xi],1);
    }
    if(a[i][j]=='S'){
      gr.add_edge(1000,xi,1000);
      gr.add_edge(1000,yi,1000);
      // cout << "sx sy " << vmap[xi] << " "  << vmap[yi] << endl;
    }
    if(a[i][j]=='T'){
      gr.add_edge(xi,1000+1,1000);
      gr.add_edge(yi,1000+1,1000);
    }
    
  }
  // cout << vertex << endl;
  // gr.max_flow(vertex,vertex+1);
  cout << gr.max_flow(1000,1000+1) << endl;
  // gr.output();

  return 0;
    

}


Measured memory_bytes: 1280