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

using i64 = int64_t;

#define rep(i, x, y) for (i64 i = i64(x), i##_max_for_repmacro = i64(y); i < i##_max_for_repmacro; ++i)
#define debug(x) #x << "=" << (x)

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#define print(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define print(x)
#endif

template <i64 p>
class fp {
    public:
    i64 x;
    fp() : x(0) {}
    fp(i64 x_) : x((x_ % p + p) % p) {}
    fp operator+() const { return fp(x); }
    fp operator-() const { return fp(-x); }
    fp& operator+=(const fp& y) {
        x += y.x;
        if (x >= p) x -= p;
        return *this;
    }
    fp& operator-=(const fp& y) { return *this += -y; }
    fp& operator*=(const fp& y) {
        x = x * y.x % p;
        return *this;
    }
    fp& operator/=(const fp& y) { return *this *= fp(inverse(y.x)); }
    fp operator+(const fp& y) const { return fp(x) += y; }
    fp operator-(const fp& y) const { return fp(x) -= y; }
    fp operator*(const fp& y) const { return fp(x) *= y; }
    fp operator/(const fp& y) const { return fp(x) /= y; }
    bool operator==(const fp& y) const { return x == y.x; }
    bool operator!=(const fp& y) const { return !(*this == y); }
    i64 extgcd(i64 a, i64 b, i64& x, i64& y) {
        i64 d = a;
        if (b != 0) {
            d = extgcd(b, a % b, y, x);
            y -= (a / b) * x;
        } else {
            x = 1;
            y = 0;
        }
        return d;
    }
    i64 inverse(i64 a) {
        i64 x, y;
        extgcd(a, p, x, y);
        return (x % p + p) % p;
    }
};

template <i64 p>
i64 abs(const fp<p>& x) { return x.x; }

template <i64 p>
istream& operator>>(istream& is, fp<p>& x) {
    is >> x.x;
    return is;
}

template <i64 p>
ostream& operator<<(ostream& os, const fp<p>& x) {
    os << x.x;
    return os;
}

template <typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
    os << "[";
    for (const auto& v : vec) {
        os << v << ",";
    }
    os << "]";
    return os;
}

template <typename T>
bool chmin(T& a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <typename A, typename T, size_t size>
void fill(A (&ary)[size], const T& val) {
    fill((T*)ary, (T*)(ary + size), val);
}

constexpr int inf = 1.01e9;
constexpr i64 inf64 = 4.01e18;
constexpr long double eps = 1e-9;

// double(64bit浮動小数)のn分探索のループ回数の上限(2分探索なら50でも十分かもしれない). long double(80ビットの x87 浮動小数点型?)だと, 2分探索であってもこれだと足りないケースがある気がするので, もうちょっと余裕を持たせた方が良さそう.
constexpr i64 max_loop = 100;

struct max_flow {
    struct edge {
        int to;
        i64 cap, rev;
    };
    vector<vector<edge>> graph;
    vector<bool> done;
    max_flow(int size) : graph(size), done(size) {}
    void add_edge(int from, int to, i64 cap) {
        graph[from].push_back(edge{to, cap, (int)graph[to].size()});
        graph[to].push_back(edge{from, 0, (int)graph[from].size() - 1});
    }
    i64 dfs(int v, int t, i64 f) {
        if (v == t) return f;
        done[v] = true;
        for (auto &e : graph[v]) {
            if (done[e.to] or e.cap <= 0) continue;
            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;
    }
    i64 calc_max_flow(int s, int t) {
        i64 flow = 0;
        while (true) {
            fill(done.begin(), done.end(), false);
            i64 f = dfs(s, t, inf);
            if (f == 0) return flow;
            flow += f;
        }
    }
};

void solve() {
    //constexpr i64 mod = 1'000'000'007;
    i64 H,W;
    cin >> H >> W;

    vector<string> a(H);
    rep(i,0,H) cin >> a[i];

    i64 sy,sx,ty,tx;
    rep(i,0,H){
        rep(j,0,W){
            if(a[i][j]=='S'){
                sy=i;
                sx=j;
            }
            if(a[i][j]=='T'){
                ty=i;
                tx=j;
            }
        }
    }

    if(sy==ty or sx==tx){
        cout << -1 << endl;
        return;
    }

    i64 s=H+W,t=H+W+1;
    max_flow mf(H+W+2);
    mf.add_edge(s,sy,inf64);
    mf.add_edge(s,sx+H,inf64);
    mf.add_edge(ty,t,inf64);
    mf.add_edge(tx+H,t,inf64);
    rep(i,0,H){
        rep(j,0,W){
            if(a[i][j]!='o') continue;
            mf.add_edge(i,j+H,1);
            mf.add_edge(j+H,i,1);
        }
    }

    cout << mf.calc_max_flow(s,t) << endl;
}

int main() {
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    cout.setf(ios::fixed);
    cout.precision(16);
    solve();
    return 0;
}


Measured memory_bytes: 1536