#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()
#define ln '\n'
constexpr long long MOD = 1000000007LL;
//constexpr long long MOD = 998244353LL;
typedef long long ll;
typedef unsigned long long ull; 
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
template<class T, class U> inline bool chmax(T &a, U b) { if (a < b) { a = b; return true;} return false; }
template<class T, class U> inline bool chmin(T &a, U b) { if (a > b) { a = b; return true;} return false; }
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

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;
      }
    }
  }
};

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int H,W; cin >> H >> W;
    vector<string> S(H);
    rep(i,H) cin >> S[i];

    int V = (H+1)*(W+1);
    Dinic<int> D(V);
    int s,t;
    rep(i,H) {
        rep(j,W) {
            if (S[i][j]=='S') {
                s = i*(W+1)+j;
                D.add_edge(s,H*(W+1)+j,10000);
                D.add_edge(H*(W+1)+j,s,10000);
                D.add_edge(s,i*(W+1)+W,10000);
                D.add_edge(i*(W+1)+W,s,10000);
            } else if (S[i][j]=='T') {
                t = i*(W+1)+j;
                D.add_edge(t,H*(W+1)+j,10000);
                D.add_edge(H*(W+1)+j,t,10000);
                D.add_edge(t,i*(W+1)+W,10000);
                D.add_edge(i*(W+1)+W,t,10000);
            } else if (S[i][j]=='o') {
                int u = i*(W+1)+j;
                D.add_edge(u,H*(W+1)+j,1);
                D.add_edge(H*(W+1)+j,u,1);
                D.add_edge(u,i*(W+1)+W,1);
                D.add_edge(i*(W+1)+W,u,1);
            }
        }
    }

    int val = D.max_flow(s,t);
    cout << (val >= 10000 ? -1 : val) << ln;
}

Measured memory_bytes: 2560