#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define all(a) (a).begin(), (a).end()
#define endl "\n"
#define rep(i, a, b) for (auto i = (a); i < (b); ++i)
#define rrep(i, a, b) for (auto i = (a); i > (b); --i)
#define UNIQUE(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

#ifdef LOCAL_DEFINE
struct InitInput
{
  InitInput()
  {
    FILE *stream1;
    stream1 = freopen("in.txt", "r", stdin);
    assert(stream1 != nullptr);
    cerr << "This problem is not interactive" << endl;
  }
} LOCAL_INPUT;
struct LOCAL_OUTPUT
{
  LOCAL_OUTPUT()
  {
    FILE *stream2;
    const char *outputfile = "out.txt";
    stream2 = freopen(outputfile, "w", stdout);
    assert(stream2 != nullptr);
    cerr << "output [ " << outputfile << " ]" << endl;
  }
} /*LOCAL_OUTPUT*/;
#define show(x) cerr << #x << " = " << (x) << " (line " << __LINE__ << ")" << endl
#define showA(a, n) \
  do{for(int i=0;i<(n);i++)cerr<<"("<<i<<" = "<<(a)[i]<<") ";cerr<<endl;}while(0)
#define showA2(a, n, m) \
  do {for(int i=0;i<(n);i++){for(int j=0;j<(m);j++){cerr<<"("<<i<<", "<<j<<" = "<<(a)[i][j]<<") ";}cerr<<endl;}cerr<<endl;}while(0)
#else
#define show(x)
#define showA(a, n)
#define showA2(a, n, m)
#endif

struct InitAim
{
  InitAim()
  {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.precision(12);
    cout << fixed;
#ifdef LOCAL_DEFINE
    cerr << "This problem is not interactive" << endl;
#endif
  }
} aim_cpo;

typedef long long ll;
typedef unsigned long long ull;

constexpr const int INT_INF = 0x3f3f3f3f;       //1061109567
constexpr const ll LL_INF = 0x3f3f3f3f3f3f3f3f; //4557430888798830399

template <typename T>
bool chmin(T &a, T b) { return a > b ? (a = b, true) : false; }
template <typename T>
bool chmax(T &a, T b) { return a < b ? (a = b, true) : false; }
template <typename T>
void ln(T i, T n) { cout << (i == n - 1 ? "\n" : " "); }
template <typename T, typename S>
ostream &operator<<(ostream &out, const pair<T, S> &pair1)
{
  out << '(' << pair1.fi << ", " << pair1.se << ')';
  return out;
}
template <typename T>
ostream &operator<<(ostream &out, const vector<T> &vector1)
{
  out << '[';
  for (unsigned int i = 0; i < vector1.size(); i++)
  {
    out << vector1[i];
    if (i == vector1.size() - 1)
      out << "]";
    else
      out << ", ";
  }
  return out;
}

// INT
#define GCD(a, b) __gcd(a, b)
template <typename T>
T LCM(T a, T b)
{
  return a / GCD(a, b) * b;
}
template <typename T>
T EXTGCD(T a, T b, T &x, T &y)
{
  T d = a;
  if (b != 0)
  {
    d = EXTGCD(b, a % b, y, x);
    y -= (a / b) * x;
  }
  else
    x = 1, y = 0;
  return d;
}
template <typename T>
bool is_prime(T a)
{
  for (int i = 2; i * i <= a; i++)
    if (a % i == 0)
      return true;
  return false;
}
template <typename T, typename S>
T Pow(T a, S b)
{
  T res = 1, now = a;
  while (b)
  {
    if (b & 1)
      res *= now;
    b >>= 1;
    now *= now;
  }
  return res;
}

// MOD
ll MOD = 1000000000L + 7L;
#define Madd(a, b) (((a) % MOD) + ((b) % MOD)) % MOD
#define Mmul(a, b) (((a) % MOD) * ((b) % MOD)) % MOD
#define Msub(a, b) (((a) % MOD) + MOD - ((b) % MOD)) % MOD
template <typename T, typename S>
T ModPow(T a, S b)
{
  assert(b >= 0);
  T res = 1, now = Msub(a, 0);
  while (b)
  {
    if (b & 1)
      res = Mmul(res, now);
    b >>= 1;
    now = Mmul(now, now);
  }
  return res;
}
template <typename T>
T ModInverse(T a, T mod, bool prime)
{ // if mod is prime, "prime" is true.
  if (prime)
    return ModPow(a, mod - 2);
  else
  {
    T x, y;
    EXTGCD(a, mod, x, y);
    return (mod + x % mod) % mod;
  }
}
template <typename T>
T EulerTotient(T a)
{
  vector<pair<int, int>> v;
  for (T i = 2; i * i <= a; i++)
  {
    int cnt = 0;
    while (a % i == 0)
    {
      cnt++;
      a /= i;
    }
    if (cnt != 0)
      v.emplace_back(i, cnt);
  }
  if (a != 1)
    v.emplace_back(a, 1);
  //showV(v, (int) v.size());
  T res = 1;
  for (int i = 0; i < (int)v.size(); i++)
  {
    if (v[i].se == 1)
    {
      //res *= v[i].fi - 1;
      res = Mmul(res, v[i].fi - 1);
    }
    else
    {
      //res *= Pow(v[i].fi, v[i].se) - Pow(v[i].fi, v[i].se - 1);
      res = Mmul(res, Msub(ModPow(v[i].fi, v[i].se), ModPow(v[i].fi, v[i].se - 1)));
    }
  }
  return res;
}
#define Mdivide(a, b) Mmul(((a) % MOD), (ModInverse((b), MOD, true))) % MOD
ll comb(ll a, ll b)
{
  chmin(b, a - b);
  ll res = 1LL, now = a;
  for (ll i = 1; i <= b; i++)
  {
    res = Mmul(res, now);  //res *= now;
    res = Mdivide(res, i); // res /= i;
    now--;
  }
  return res;
}

///////////////////////////////////////////////////////////////////////////////////
// TEMPLATE(data structure)
///////////////////////////////////////////////////////////////////////////////////

template <typename T>
class BIT
{
public:
  BIT(int size)
  {
    BITTable.assign(++size, 0);
  }
  T sum(int k)
  {
    T res = 0;
    for (++k; k > 0; k -= k & -k)
    {
      res += BITTable[k];
    }
    return res;
  }
  T sum(int l, int r)
  {
    if (l == 0)
      return sum(r);
    return sum(r) - sum(l - 1);
  }
  void update(int k, T x)
  { // b[k] += x;
    for (++k; k < (int)BITTable.size(); k += k & -k)
      BITTable[k] += x;
  }

private:
  vector<T> BITTable;
};

template <typename T>
class IntervalTree
{
  using F = function<T(T, T)>;

public:
  IntervalTree(int n, const F func, const T init) : func(func), init(init)
  {
    size = 1;
    while ((int)size < n)
      size <<= 1;
    table.assign(2 * size, init);
  }
  void set(int k, T &x)
  {
    table[size + k] = x;
  }
  void build()
  {
    for (int i = size - 1; i >= 0; --i)
    {
      table[i] = func(table[i * 2], table[i * 2 + 1]);
    }
  }
  void update(int k, const T &x)
  {
    k += size;
    table[k] = x;
    while (k >>= 1)
    {
      table[k] = func(table[k * 2], table[k * 2 + 1]);
    }
  }
  T query(int a, int b)
  {
    T L = init, R = init;
    for (a += size, b += size; a < b; a >>= 1, b >>= 1)
    {
      if (a & 1)
        L = func(L, table[a++]);
      if (b & 1)
        R = func(table[--b], R);
    }
    return func(L, R);
  }
  T operator[](const int k) const
  {
    return table[k + size];
  }

private:
  unsigned int size;
  vector<T> table;
  const F func;
  const T init;
};

class UnionFind
{
public:
  explicit UnionFind(int _n) : n(_n)
  {
    par.resize(static_cast<unsigned long>(_n));
    rank.resize(static_cast<unsigned long>(_n));
    sizes.resize(static_cast<unsigned long>(_n));
    for (int i = 0; i < _n; i++)
    {
      par[i] = i;
      rank[i] = 0;
      sizes[i] = 1;
    }
  }
  int find(int a)
  {
    if (par[a] == a)
      return a;
    return par[a] = find(par[a]);
  }
  bool same(int a, int b)
  {
    return find(a) == find(b);
  }
  void unite(int a, int b)
  {
    link(find(a), find(b));
  }
  int size(int a)
  {
    return sizes[find(a)];
  }
  void view()
  {
    for (int i = 0; i < n; i++)
    {
      cout << " par"
           << "[" << i << "]=" << par[i] << ((i == n - 1) ? "\n" : ",");
    }
    for (int i = 0; i < n; i++)
    {
      cout << "size"
           << "[" << i << "]=" << sizes[i] << ((i == n - 1) ? "\n" : ",");
    }
    cout << endl;
  }

private:
  void link(int a, int b)
  {
    if (same(a, b))
      return;
    if (rank[a] > rank[b])
    {
      par[b] = a;
      sizes[a] += sizes[b];
      sizes[b] = 0;
    }
    else
    {
      par[a] = b;
      if (rank[a] == rank[b])
        rank[b]++;
      sizes[b] += sizes[a];
      sizes[a] = 0;
    }
  }
  int n;
  vector<int> par;
  vector<int> rank;
  vector<int> sizes;
};

template<typename T>
class Dinic{
public:
  Dinic(int SIZE) :SIZE(SIZE) {
    v = vector<vector<tuple<int, int, T>>>(SIZE + 10);
  }
  void AddEdge(int from, int to, int cap) {
    v[from].push_back(make_tuple(to, cap, v[to].size()));
    v[to].push_back(make_tuple(from, 0, v[from].size() - 1));
  }

  void bfs(int s) {
    level = vector<int>(SIZE + 10, -1);
    queue<int> q;
    level[s] = 0;
    q.push(s);
    while (!q.empty()) {
      int now = q.front(); q.pop();
      for (int i = 0; i < (int)v[now].size(); i++) {
        int next, nextc, nextrv; tie(next, nextc, nextrv) = v[now][i];
        if (nextc > 0 && level[next] < 0) {
          level[next] = level[now] + 1;
          q.push(next);
        }
      }
    }
  }

  int dfs(int now, int t, int f) {
    if (now == t) return f;
    for (int &i = iter[now]; i < (int)v[now].size(); i++) {
      int next, nextc, nextrv; tie(next, nextc, nextrv) = v[now][i];
      if (nextc > 0 && level[now] < level[next]) {
        int d = dfs(next, t, min(f, nextc));
        if (d > 0) {
          get<1>(v[now][i]) -= d;
          get<1>(v[next][nextrv]) += d;
          return d;
        }
      }
    }
    return 0;
  }

  int max_flow(int s, int t) {
    int flow = 0;
    for (;;) {
      bfs(s);
      if (level[t] < 0) return flow;
      iter = vector<int>(SIZE + 10, 0);
      int f;
      while ((f = dfs(s, t, INT_MAX)) > 0) {
        flow += f;
      }
    }
  }
private:
  int SIZE;
  vector<vector<tuple<int, int, T>>> v;
  vector<int> level, iter;
};

///////////////////////////////////////////////////////////////////////////////////
// MAIN
///////////////////////////////////////////////////////////////////////////////////
// 735134400 約数が1344個ある高度合成数(<= 1e9)
// 897612484786617600 約数が103680個ある高度合成数(<= 1e18)
// 苦手分野 重複順列
// LLの数値をつかう時は最後にLLをつける癖をつけよう

int h, w;
char a[101][101];

int main()
{
  cin >> h >> w;
  rep(i, 0, h) rep(j, 0, w) cin >> a[i][j];
  Dinic<int> mf(h + w);
  int si, sj, ti, tj;
  rep(i, 0, h) rep(j, 0, w) {
    if (a[i][j] == 'S') si = i, sj = j;
    else if (a[i][j] == 'T') ti = i, tj = j;
  }
  if (si == ti || sj == tj) {
    cout << -1 << endl;
    return 0;
  }
  int s = w + h, t = w + h + 1;
  rep(i, 0, h) rep(j, 0, w) {
    if (a[i][j] == 'S') {
      mf.AddEdge(s, i, INT_MAX);
      mf.AddEdge(s, h + j, INT_MAX);
    } else if (a[i][j] == 'T') {
      mf.AddEdge(i, t, INT_MAX);
      mf.AddEdge(h + j, t, INT_MAX);
    }
  }
  rep(i, 0, h) {
    rep(j, 0, w) {
      if (a[i][j] == 'o') {
        mf.AddEdge(i, h + j, 1);
        mf.AddEdge(h + j, i, 1);
      }
    }
  }
  cout << mf.max_flow(s, t) << endl;
#ifdef LOCAL_DEFINE
  cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << "s." << endl;
  show(MOD);
#endif
  return 0;
}

///////////////////////////////////////////////////////////////////////////////////
// NOTE
///////////////////////////////////////////////////////////////////////////////////
/*
max flowなんだけど、辺の貼り方をしっかり考える.
横と縦に自由に移動することができるので、a[i][j] == 'o'のときは
a[i][j]の葉を取ると、a[i][k]からa[l][j](0<=k<w, 0<=l<h)に移動することができなくなる.
なので、flowをする際の頂点はS, T, 各列と各行の分だけ作る必要がある.(全部のマス目分は必要ない)
SとTは取ることができないので、別途頂点にし、Sからの辺とTへの辺はINFにする必要がある
(どう頑張っても水は流れる).
a[i][j]の葉を取ると、i行目の葉からj列目の葉に移動できなくなるので、i行目の頂点からj列目の
頂点への辺をカットすることができる(逆も成り立つ、すなわち無向辺).
葉を取るコストは1なのでcapを1として辺を貼っておく.
こうしてできたグラフにSからTへのmax flowを求めると答え.
全部のマス目を用意すると、行と列の処理の仕方がわからないので、今回みたいに行全体、列全体に操作できる
ような問題は頂点を行ごと列ごとに持っておくときれいに書けるのかな.
なんにせよフロー面白いわ.
*/

Measured memory_bytes: 896