// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using i32 = int32_t;
using i64 = int64_t;
#define int ll
#define double ld
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define rep1(i,n) for (int i = 1; i <= (int)(n); i++)
#define repR(i,n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep1R(i,n) for (int i = (int)(n); i >= 1; i--)
#define loop(i,a,B) for (int i = a; i B; i++)
#define loopR(i,a,B) for (int i = a; i B; i--)
#define all(x) (x).begin(), (x).end()
#define allR(x) (x).rbegin(), (x).rend()
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
auto constexpr INF32 = numeric_limits<int32_t>::max()/2-1;
auto constexpr INF64 = numeric_limits<int64_t>::max()/2-1;
auto constexpr INF   = numeric_limits<int>::max()/2-1;
#ifdef LOCAL
#include "debug.hpp"
#define dump(...) cerr << "[" << setw(3) << __LINE__ << ":" << __FUNCTION__ << "] ", dump_impl(#__VA_ARGS__, __VA_ARGS__)
#define say(x) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] " << x << endl
#define debug if (1)
#else
#define dump(...) (void)(0)
#define say(x) (void)(0)
#define debug if (0)
#endif
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T> >;
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
ostream& operator<<(ostream& os, T const& v) { bool f = true; for (auto const& x : v) os << (f ? "" : " ") << x, f = false; return os; }
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
istream& operator>>(istream& is, T &v) { for (auto& x : v) is >> x; return is; }
template <class T, class S> istream& operator>>(istream& is, pair<T,S>& p) { return is >> p.first >> p.second; }
struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup;
template <class F> struct FixPoint : private F {
    constexpr FixPoint(F&& f) : F(forward<F>(f)) {}
    template <class... T> constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward<T>(x)...); }
};
struct MakeFixPoint {
    template <class F> constexpr auto operator|(F&& f) const { return FixPoint<F>(forward<F>(f)); }
};
#define MFP MakeFixPoint()|
#define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__)
template <class T, size_t d> struct vec_impl {
    using type = vector<typename vec_impl<T,d-1>::type>;
    template <class... U> static type make_v(size_t n, U&&... x) { return type(n, vec_impl<T,d-1>::make_v(forward<U>(x)...)); }
};
template <class T> struct vec_impl<T,0> { using type = T; static type make_v(T const& x = {}) { return x; } };
template <class T, size_t d = 1> using vec = typename vec_impl<T,d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args&&... args) { return vec_impl<T,d>::make_v(forward<Args>(args)...); }
template <class T> void quit(T const& x) { cout << x << endl; exit(0); }
template <class T> constexpr bool chmin(T& x, T const& y) { if (x > y) { x = y; return true; } return false; }
template <class T> constexpr bool chmax(T& x, T const& y) { if (x < y) { x = y; return true; } return false; }
template <class It> constexpr auto sumof(It b, It e) { return accumulate(b,e,typename iterator_traits<It>::value_type{}); }
template <class T> int sz(T const& x) { return x.size(); }
template <class C, class T> int lbd(C const& v, T const& x) {
    return lower_bound(v.begin(), v.end(), x)-v.begin();
}
template <class C, class T> int ubd(C const& v, T const& x) {
    return upper_bound(v.begin(), v.end(), x)-v.begin();
}
template <class C, class F> int ppt(C const& v, F f) {
    return partition_point(v.begin(), v.end(), f)-v.begin();
}
// <<<
// >>> Dinic
template <class Flow>
struct Dinic {
    static constexpr Flow INF = numeric_limits<Flow>::max();
    static constexpr Flow EPS = 1e-10; //

    struct edge {
        int32_t to,rev;
        Flow cap;
        edge(int to, int rev, Flow cap) : to(to), rev(rev), cap(cap) {}
    };
    vector<vector<edge>> g;
    vector<pair<int32_t,int32_t>> es;
    vector<int32_t> level, iter;
    int n,s,t;

    Dinic(int n) : g(n),n(n) {}
    void add_edge(int from, int to, Flow cap) {
        es.emplace_back(from, g[from].size());
        g[from].emplace_back(to, g[to].size(), cap);
        g[to].emplace_back(from, g[from].size()-1, 0);
    }

    bool bfs() {
        level.assign(n,-1);
        queue<int> q;
        level[s] = 0;
        q.push(s);
        while (q.size() && level[t] < 0) {
            int x = q.front(); q.pop();
            for (auto const& e : g[x]) {
                if (e.cap > EPS && level[e.to] < 0) {
                    level[e.to] = level[x] + 1;
                    q.push(e.to);
                }
            }
        }
        return level[t] >= 0;
    }

    Flow dfs(int x, Flow f = INF) {
        if (x == t) return f;
        Flow res = 0;
        for (auto &i = iter[x]; i < int(g[x].size()); ++i) {
            auto &e = g[x][i];
            if (e.cap > EPS && level[x] < level[e.to]) {
                Flow d = dfs(e.to, min(f,e.cap));
                e.cap -= d;
                g[e.to][e.rev].cap += d;
                res += d;
                f -= d;
                if (f == 0) break;
            }
        }
        return res;
    }

    Flow max_flow(int s, int t) {
        assert(0 <= s); assert(s < n);
        assert(0 <= t); assert(t < n);
        this-> s = s; this->t = t;
        Flow flow = 0;
        while (bfs()) {
            iter.assign(n,0);
            for (Flow f = 0; (f = dfs(s)); flow += f) {}
        }
        return flow;
    }

    void output() const {
        cerr << "dinic output:" << endl;
        for (auto const& p : es) {
            auto const& e = g[p.first][p.second];
            auto const& r = g[e.to][e.rev];
            cerr << p.first << "->" << e.to << " : "
                 << r.cap << "/" << e.cap+r.cap << endl;
        }
    }

};
// <<<

int32_t main() {
    int h,w; cin >> h >> w;
    vector<string> a(h); cin >> a;

    Dinic<int> g(h+w+2);
    int s = h+w, t = s+1;
    rep (i,h) rep (j,w) {
        if (a[i][j] == 'S') {
            g.add_edge(s,i,INF);
            g.add_edge(s,h+j,INF);
        }
        if (a[i][j] == 'T') {
            g.add_edge(i,t,INF);
            g.add_edge(h+j,t,INF);
        }
        if (a[i][j] == 'o') {
            g.add_edge(i,h+j,1);
            g.add_edge(h+j,i,1);
        }
    }

    int ans = g.max_flow(s,t);
    if (ans >= INF) ans = -1;
    cout << ans << endl;
}


Measured memory_bytes: 1280