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

#pragma region Template

// Define
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T> using pvector = vector<pair<T, T>>;
template <class T> using rpriority_queue = priority_queue<T, vector<T>, greater<T>>;
constexpr const ll dx[4] = {1, 0, -1, 0};
constexpr const ll dy[4] = {0, 1, 0, -1};
constexpr const ll MOD = 1e9 + 7;
constexpr const ll mod = 998244353;
constexpr const ll INF = 1LL << 60;
constexpr const ll inf = 1 << 30;
constexpr const char rt = '\n';
constexpr const char sp = ' ';
#define rt(i, n) (i == (ll)(n) -1 ? rt : sp)
#define len(x) ((ll)(x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define ifn(x) if (not(x))
#define elif else if
#define elifn else ifn
#define fi first
#define se second
#define uniq(x) (sort(all(x)), (x).erase(unique(all(x)), (x).end()))

using graph = vector<vector<ll>>;
template <class T> using wgraph = vector<vector<ll, T>>;
bool __DIRECTED__ = true;
istream &operator>>(istream &is, graph &g) {
    ll a, b;
    is >> a >> b;
    g[a - 1].pb(b - 1);
    if (__DIRECTED__ == false) g[b - 1].pb(a - 1);
    return is;
}
template <class T> istream &operator>>(istream &is, wgraph<T> &g) {
    ll a, b;
    T c;
    is >> a >> b >> c;
    g[a - 1].pb({b - 1, c});
    if (__DIRECTED__ == false) g[b - 1].pb({a - 1, c});
    return is;
}

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 (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

// Debug
#define debug(...)                                                                                 \
    {                                                                                              \
        cerr << __LINE__ << ": " << #__VA_ARGS__ << " = ";                                         \
        for (auto &&__i : {__VA_ARGS__}) cerr << "[" << __i << "] ";                               \
        cerr << rt;                                                                                \
    }

#define dump(a, h, w)                                                                              \
    {                                                                                              \
        cerr << __LINE__ << ": " << #a << " = [" << rt;                                            \
        rep(__i, h) {                                                                              \
            rep(__j, w) {                                                                          \
                if (abs(a[__i][__j]) >= INF / 2 and a[__i][__j] <= -INF / 2) cerr << '-';          \
                if (abs(a[__i][__j]) >= INF / 2) cerr << "∞" << sp;                                \
                else                                                                               \
                    cerr << a[__i][__j] << sp;                                                     \
            }                                                                                      \
            cerr << rt;                                                                            \
        }                                                                                          \
        cerr << "]" << rt;                                                                         \
    }

#define vdump(a, n)                                                                                \
    {                                                                                              \
        cerr << __LINE__ << ": " << #a << " = [";                                                  \
        rep(__i, n) {                                                                              \
            if (__i) cerr << sp;                                                                   \
            if (abs(a[__i]) >= INF / 2 and a[__i] <= -INF / 2) cerr << '-';                        \
            if (abs(a[__i]) >= INF / 2) cerr << "∞" << sp;                                         \
            else                                                                                   \
                cerr << a[__i];                                                                    \
        }                                                                                          \
        cerr << "]" << rt;                                                                         \
    }

// Loop
#define inc(i, a, n) for (ll i = (a), _##i = (n); i <= _##i; ++i)
#define dec(i, a, n) for (ll i = (a), _##i = (n); i >= _##i; --i)
#define rep(i, n) for (ll i = 0, _##i = (n); i < _##i; ++i)
#define each(i, a) for (auto &&i : a)

// Stream
#define fout(n) cout << fixed << setprecision(n)
struct io {
    io() { cin.tie(nullptr), ios::sync_with_stdio(false); }
} io;

/*
// Speed
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunknown-pragmas"
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target(                                                                                \
    "sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native,arch=skylake-avx512")
#pragma GCC diagnostic pop
*/

// Math
inline constexpr ll gcd(const ll a, const ll b) { return b ? gcd(b, a % b) : a; }
inline constexpr ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }

inline constexpr ll modulo(const ll n, const ll m = MOD) {
    ll k = n % m;
    return k + m * (k < 0);
}
inline constexpr ll chmod(ll &n, const ll m = MOD) {
    n %= m;
    return n += m * (n < 0);
}
inline constexpr ll mpow(ll a, ll n, const ll m = MOD) {
    ll r = 1;
    rep(i, 64) {
        if (n & (1LL << i)) r *= a;
        chmod(r, m);
        a *= a;
        chmod(a, m);
    }
    return r;
}
inline ll inv(const ll n, const ll m = MOD) {
    ll a = n, b = m, x = 1, y = 0;
    while (b) {
        ll t = a / b;
        a -= t * b;
        swap(a, b);
        x -= t * y;
        swap(x, y);
    }
    return modulo(x, m);
}

#pragma endregion

struct Dinic {
    struct edge {
        int to, cap, rev;
    };
    int V;
    vector<vector<edge>> graph;
    vector<int> itr, level;

    Dinic(int V) : V(V) { graph.assign(V, vector<edge>()); }

    void add_edge(int from, int to, int cap) {
        graph[from].push_back((edge){to, cap, (int) graph[to].size()});
        graph[to].push_back((edge){from, 0, (int) graph[from].size() - 1});
    }

    void bfs(int s) {
        level.assign(V, -1);
        queue<int> q;
        level[s] = 0;
        q.push(s);
        while (!q.empty()) {
            int v = q.front();
            q.pop();
            for (auto &e : graph[v]) {
                if (e.cap > 0 and level[e.to] < 0) {
                    level[e.to] = level[v] + 1;
                    q.push(e.to);
                }
            }
        }
    }

    int dfs(int v, int t, int f) {
        if (v == t) return f;
        for (int &i = itr[v]; i < (int) graph[v].size(); ++i) {
            edge &e = graph[v][i];
            if (e.cap > 0 and level[v] < level[e.to]) {
                int d = dfs(e.to, t, min(f, e.cap));
                if (d > 0) {
                    e.cap -= d;
                    graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

    int max_flow(int s, int t) {
        int ret = 0, f;
        while (bfs(s), level[t] >= 0) {
            itr.assign(V, 0);
            while ((f = dfs(s, t, inf)) > 0) ret += f;
        }
        return ret;
    }
};

signed main() {
    ll H, W;
    cin >> H >> W;
    string S[H];
    rep(i, H) cin >> S[i];
    Dinic D(H + W + 2);
    rep(i, H) rep(j, W) {
        if (S[i][j] == 'S') {
            D.add_edge(0, 1 + i, inf);
            D.add_edge(0, H + 1 + j, inf);
        }
        if (S[i][j] == 'T') {
            D.add_edge(1 + i, H + W + 1, inf);
            D.add_edge(H + 1 + j, H + W + 1, inf);
        }
        if (S[i][j] == 'o') {
            D.add_edge(1 + i, H + 1 + j, 1);
            D.add_edge(H + 1 + j, 1 + i, 1);
        }
    }
    ll f = D.max_flow(0, H + W + 1);
    if (f >= inf) {
        cout << -1 << rt;
    } else {
        cout << f << rt;
    }
}

Measured memory_bytes: 4024