#include <bits/stdc++.h>
#include <sys/time.h>
using namespace std;

#define rep(i,n) for(long long i = 0; i < (long long)(n); i++)
#define repi(i,a,b) for(long long i = (long long)(a); i < (long long)(b); i++)
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define mt make_tuple
#define mp make_pair
template<class T1, class T2> bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

using ll = int; using vll = vector<ll>; using vvll = vector<vll>; using P = pair<ll, ll>;
using ld = long double;  using vld = vector<ld>; 
using vi = vector<int>; using vvi = vector<vi>; vll conv(vi& v) { vll r(v.size()); rep(i, v.size()) r[i] = v[i]; return r; }

inline void input(int &v){ v=0;char c=0;int p=1; while(c<'0' || c>'9'){if(c=='-')p=-1;c=getchar();} while(c>='0' && c<='9'){v=(v<<3)+(v<<1)+c-'0';c=getchar();} v*=p; } // これを使うならば、tieとかを消して！！
template <typename T, typename U> ostream &operator<<(ostream &o, const pair<T, U> &v) {  o << "(" << v.first << ", " << v.second << ")"; return o; }
template<size_t...> struct seq{}; template<size_t N, size_t... Is> struct gen_seq : gen_seq<N-1, N-1, Is...>{}; template<size_t... Is> struct gen_seq<0, Is...> : seq<Is...>{};
template<class Ch, class Tr, class Tuple, size_t... Is>
void print_tuple(basic_ostream<Ch,Tr>& os, Tuple const& t, seq<Is...>){ using s = int[]; (void)s{0, (void(os << (Is == 0? "" : ", ") << get<Is>(t)), 0)...}; }
template<class Ch, class Tr, class... Args> 
auto operator<<(basic_ostream<Ch, Tr>& os, tuple<Args...> const& t) -> basic_ostream<Ch, Tr>& { os << "("; print_tuple(os, t, gen_seq<sizeof...(Args)>()); return os << ")"; }
ostream &operator<<(ostream &o, const vvll &v) { rep(i, v.size()) { rep(j, v[i].size()) o << v[i][j] << " "; o << endl; } return o; }
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T> ostream &operator<<(ostream &o, const deque<T> &v) { o << '['; rep(i, v.size()) o << v[i] << (i != v.size()-1 ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T>  ostream &operator<<(ostream &o, const unordered_set<T> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U>  ostream &operator<<(ostream &o, const map<T, U> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it << (next(it) != m.end() ? ", " : ""); o << "]";  return o; }
template <typename T, typename U, typename V>  ostream &operator<<(ostream &o, const unordered_map<T, U, V> &m) { o << '['; for (auto it = m.begin(); it != m.end(); it++) o << *it; o << "]";  return o; }
vector<int> range(const int x, const int y) { vector<int> v(y - x + 1); iota(v.begin(), v.end(), x); return v; }
template <typename T> istream& operator>>(istream& i, vector<T>& o) { rep(j, o.size()) i >> o[j]; return i;}
template <typename T, typename S, typename U> ostream &operator<<(ostream &o, const priority_queue<T, S, U> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const queue<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.front(); tmp.pop(); o << x << " ";} return o; }
template <typename T> ostream &operator<<(ostream &o, const stack<T> &v) { auto tmp = v; while (tmp.size()) { auto x = tmp.top(); tmp.pop(); o << x << " ";} return o; }
template <typename T> unordered_map<T, ll> counter(vector<T> vec){unordered_map<T, ll> ret; for (auto&& x : vec) ret[x]++; return ret;};
string substr(string s, P x) {return s.substr(x.fi, x.se - x.fi); }
void vizGraph(vvll& g, int mode = 0, string filename = "out.png") { ofstream ofs("./out.dot"); ofs << "digraph graph_name {" << endl; set<P> memo; rep(i, g.size())  rep(j, g[i].size()) { if (mode && (memo.count(P(i, g[i][j])) || memo.count(P(g[i][j], i)))) continue; memo.insert(P(i, g[i][j])); ofs << "    " << i << " -> " << g[i][j] << (mode ? " [arrowhead = none]" : "")<< endl;  } ofs << "}" << endl; ofs.close(); system(((string)"dot -T png out.dot >" + filename).c_str()); }
size_t random_seed; namespace std { using argument_type = P; template<> struct hash<argument_type> { size_t operator()(argument_type const& x) const { size_t seed = random_seed; seed ^= hash<ll>{}(x.fi); seed ^= (hash<ll>{}(x.se) << 1); return seed; } }; }; // hash for various class
struct timeval start; double sec() { struct timeval tv; gettimeofday(&tv, NULL); return (tv.tv_sec - start.tv_sec) + (tv.tv_usec - start.tv_usec) * 1e-6; }
struct init_{init_(){ ios::sync_with_stdio(false); cin.tie(0); gettimeofday(&start, NULL); struct timeval myTime; struct tm *time_st; gettimeofday(&myTime, NULL); time_st = localtime(&myTime.tv_sec); srand(myTime.tv_usec); random_seed = RAND_MAX / 2 + rand() / 2; }} init__;
#define ldout fixed << setprecision(40) 

#define INF (ll)1e9
#define mo  (ll)(1e9+7)


#define FORR(x,arr) for(auto& x:arr)
#define ZERO(a) memset(a,0,sizeof(a))
template<class V> class MaxFlow_Ford {
    public:
        struct edge { int to,reve;V cap;};
        static const int MV = 20002; // 頂点数
        vector<edge> E[MV];
        int vis[MV];
        void add_edge(int x,int y,V cap,bool undir=false) {
            E[x].push_back((edge){y,(int)E[y].size(),cap});
            E[y].push_back((edge){x,(int)E[x].size()-1,undir?cap:0});
        }
        V dfs(int from,int to,V cf) {
            V tf;
            if(from==to) return cf;
            vis[from]=1;
            FORR(e,E[from]) if(vis[e.to]==0 && e.cap>0 && (tf = dfs(e.to,to,min(cf,e.cap)))>0) {
                e.cap -= tf;
                E[e.to][e.reve].cap += tf;
                return tf;
            }
            return 0;
        }
        V maxflow(int from, int to) {
            V fl=0,tf;
            while(1) {
                ZERO(vis);
                if((tf = dfs(from,to,numeric_limits<V>::max()))==0) return fl;
                fl+=tf;
            }
        }
};

#define pos(i, j) (2*((i)*W+j))
int main(void) {
    ll H, W; cin >> H >> W;
    vector<string> b(H);
    rep(i, H) cin >> b[i];

    ll sx = -1, sy = -1, tx = -1, ty = -1;
    rep(h, H) rep(w, W) {
        if (b[h][w] == 'S') {
            sx = h, sy = w;
        } 
        if (b[h][w] == 'T') {
            tx = h, ty = w;
        } 
    }
    if (sx == tx || sy == ty) {
        cout << -1 << endl;
        return 0;
    }

    MaxFlow_Ford<ll> ff;

    ll src = 2*H*W;
    ll dst = 2*H*W+1;

    // inner edges
    rep(h, H) rep(w, W) if (b[h][w] == 'o') {
        ff.add_edge(pos(h, w), pos(h, w) + 1, 1);
    }

    // Outer edges
    rep(h, H) rep(w, W) if (b[h][w] == 'o') {
        rep(nh, H) if (b[nh][w] == 'o') {
            ff.add_edge(pos(h, w) + 1, pos(nh, w), INF);
        } 
        rep(nw, W) if (b[h][nw] == 'o') {
            ff.add_edge(pos(h, w) + 1, pos(h, nw), INF);
        }
    }


    // src, dst
    rep(h, H) rep(w, W) {
        if (b[h][w] == 'S') {
            rep(nh, H) if (b[nh][w] == 'o') {
                ff.add_edge(src, pos(nh, w), INF);
            } 
            rep(nw, W) if (b[h][nw] == 'o') {
                ff.add_edge(src, pos(h, nw), INF);
            }
        }
        if (b[h][w] == 'T') {
            rep(nh, H) if (b[nh][w] == 'o') {
                ff.add_edge(pos(nh, w) + 1, dst, INF);
            } 
            rep(nw, W) if (b[h][nw] == 'o') {
                ff.add_edge(pos(h, nw) + 1, dst, INF);
            }
        }
    }


    //    vizGraph(g, 2, 1);
    cout << ff.maxflow(src, dst) << endl;

    return 0;
}


Measured memory_bytes: 62972