#define ONLINE_JUDGE
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pl;
typedef vector<pl> vp;
const ll INF=1001001001;
const ll LINF=1001001001001001001;
const ll D4[]={0,1,0,-1,0};
const ll D8[]={0,1,1,0,-1,-1,1,-1,0};
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) for(ll i=0;i<(n);++i)
#define _rep3(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2)(__VA_ARGS__)
#define _repe2(i,n) for(ll i=0;i<=(n);++i)
#define _repe3(i,a,b) for(ll i=(a);i<=(b);++i)
#define repe(...) _overload3(__VA_ARGS__,_repe3,_repe2)(__VA_ARGS__)
#define _rrep2(i,n) for(ll i=(n)-1;i>=0;i--)
#define _rrep3(i,a,b) for(ll i=(b)-1;i>=(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2)(__VA_ARGS__)
#define all(x) (x).begin(),(x).end()
template<class T>
bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>
bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}
template<class T>
using pq=priority_queue<T,vector<T>,greater<T>>;


void solve();

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

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;
      }
    }
  }
};


void solve(){
    ll h,w;cin>>h>>w;
    vector<string> a(h);
    rep(i,h)cin>>a[i];

    ll sy,sx,ty,tx;
    rep(i,h)rep(j,w){
        if(a[i][j]=='S')sy=i,sx=j;
        if(a[i][j]=='T')ty=i,tx=j;
    }

    if(sy==ty||sx==tx){
        cout<<-1<<endl;
        return;
    }

    Dinic<ll> g(h*w+h+w);
    rep(i,h)rep(j,w){
        if(a[i][j]!='o')continue;
        g.add_edge(i*w+j,h*w+i,1);
        g.add_edge(h*w+i,i*w+j,1);
        g.add_edge(i*w+j,h*w+h+j,1);
        g.add_edge(h*w+h+j,i*w+j,1);
        if(i==sy||j==sx){
            g.add_edge(sy*w+sx,i*w+j,1);
        }
        if(i==ty||j==tx){
            g.add_edge(i*w+j,ty*w+tx,1);
        }
    }
    cout<<g.max_flow(sy*w+sx,ty*w+tx)<<endl;
}


Measured memory_bytes: 3712