///////////////////////////////////////////////////////////////////////////////

#include <bits/stdc++.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

#define DEBUG 0

#define pb push_back
#define V vector
#define M unordered_map
#define S static

#define rep(i,n) for(ll i=0LL; i<n; ++i)
#define srep(i,s,n) for(ll i=s; i<n; ++i)
#define rrep(i,n) for(ll i=n-1LL; i>=0LL; --i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CIN(x) do { \
        assert(!cin.eof()); \
        cin >> x; \
        assert(!cin.fail()); \
} while(0);
#if DEBUG
#define debug_print(...) _debug_print(__VA_ARGS__)
#define debug_printf(...) printf(__VA_ARGS__)
#define debug_print_time _debug_print_time
#else // DEBUG
#define debug_print(...)
#define debug_printf(...)
#define debug_print_time
#endif // DEBUG

typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll, ll> t2;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;
template <typename T>
using priority_queue_incr = priority_queue<T, V<T>, greater<T> >;

///////////////////////////////////////////////////////////////////////////////

template <typename TT, typename T>
T get_m(M<TT, T> &m, TT k, T default_value)
{
    if (m.find(k) == m.end()) return m[k] = default_value;
    return m[k];
}

template <typename TT, typename T>
void incr_m(M<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

template <typename TT, typename T>
void incr_m(map<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

void llin(ll &a)
{
    CIN(a);
}

void llinl1(V<ll> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a;
        CIN(a);
        v.push_back(a);
    }
}

void llinl2(V<t2> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b;
        CIN(a >> b);
        v.push_back(t2(a, b));
    }
}

void llinl3(V<t3> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c;
        CIN(a >> b >> c);
        v.push_back(t3(a, b, c));
    }
}

void llinl4(V<t4> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c, d;
        CIN(a >> b >> c >> d);
        v.push_back(t4(a, b, c, d));
    }
}

void llina(V<ll> &v, ll count)
{
    llinl1(v, count);
}

template <typename T>
void sort(V<T> &v)
{
    sort(v.begin(), v.end());
}

template <typename T>
void sort_reverse(V<T> &v)
{
    sort(v.begin(), v.end(), greater<T>());
}

template <typename T>
void _debug_print(T x)
{
    cout << x << endl;
}

void _debug_print(const t2 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    cout << "-- " << x1 << " -- " << x2 << endl;
}

void _debug_print(const t3 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    cout << "-- " << x1 << " -- " << x2 << " -- " << x3 << endl;
}

void _debug_print(const t4 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    ll x4 = get<3>(x);
    cout << "-- " << x1 << " -- " << x2
         << " -- " << x3 << " -- " << x4 << endl;
}

template <typename T>
void _debug_print(T xarray[], ll n)
{
    rep (i, n) _debug_print(xarray[i]);
}

template <typename T>
void _debug_print(const V<T> &xlist)
{
    for (auto x : xlist) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename T>
void _debug_print(const set<T> &xset)
{
    for (auto x : xset) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename TT, typename T>
void _debug_print(const M<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

template <typename TT, typename T>
void _debug_print(const map<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

void _debug_print_time(const char *prefix)
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
#if DEBUG
    struct tm *tm = localtime(&tv.tv_sec);
#endif
    debug_printf("-- %s %02d:%02d:%02d.%06ld\n",
                  prefix, tm->tm_hour, tm->tm_min, tm->tm_sec, tv.tv_usec);
}

///////////////////////////////////////////////////////////////////////////////

void _main();
int main()
{
    cout << setprecision(12);
#if !DEBUG
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif

    _main();
    return 0;
}






struct MaxFlow {
    V<ll> *links;
    ll **capacities;
    ll *idxs;
    ll nodes;

    MaxFlow(ll nodes) {
        // i == 0       --> S
        // i == nodes+1 --> T
        links = new V<ll>[nodes+2LL];
        capacities = new ll*[nodes+2LL];
        rep (i, nodes+2LL) {
            capacities[i] = new ll[nodes+2LL];
            memset(capacities[i], 0, (nodes+2LL) * sizeof(ll));
        }
        idxs = new ll[nodes+2LL];
        memset(idxs, 0, (nodes+2LL) * sizeof(ll));
        this->nodes = nodes;
    }

    void add_link(ll a, ll b, ll capacity) {
        links[a].pb(b);
        links[b].pb(a);
        capacities[a][b] = capacity;
        // capacities[b][a] = 0LL;
    }

    bool find_path(deque<ll> &path, set<ll> &checked, ll v) {
        if (checked.find(v) != checked.end()) return false;

        checked.insert(v);
        path.push_back(v);
        if (v == nodes+1LL) return true;

        rep (xxx, links[v].size()) {
            ll nowidx = idxs[v]++;
            nowidx %= links[v].size();
            ll nv = links[v][nowidx];
            if (capacities[v][nv] == 0) continue;
            if (find_path(path, checked, nv)) return true;
        }

        // checked.erase(v);
        path.pop_back();
        return false;
    }

    ll solve(void) {
        ll ret = 0LL;

        for ( ; ; ) {

            set<ll> checked;
            deque<ll> foundq;
            if (!find_path(foundq, checked, 0)) break;

            V<ll> found;
            while (foundq.size()) {
                ll v = foundq.front(); foundq.pop_front();
                found.pb(v);
            }

            ll flowcount = 1e18;
            rep (i, (ll)found.size()-1LL) {
                ll src = found[i];
                ll dst = found[i+1];
                flowcount = min(flowcount, capacities[src][dst]);
            }
            assert(flowcount > 0LL);

            rep (i, (ll)found.size()-1LL) {
                ll src = found[i];
                ll dst = found[i+1];
                capacities[src][dst] -= flowcount;
                capacities[dst][src] += flowcount;
            }
            ret += flowcount;

        }

        return ret;
    }
};







void _main()
{
    ll h; llin(h);
    ll w; llin(w);
    S V<string> grid;
    rep (i, h) {
        string tmp; CIN(tmp);
        grid.pb(tmp);
    }

    ll nodes = h + w;
    ll s = 0LL;
    ll t = nodes + 1;
    MaxFlow mf(nodes);

    rep (hh, h) rep (ww, w) {
        char c = grid[hh][ww];
        if (c == 'S') {
            mf.add_link(s, hh + 1LL, 1e18);
            mf.add_link(s, h + ww + 1LL, 1e18);
        }
        if (c == 'T') {
            mf.add_link(hh + 1LL, t, 1e18);
            mf.add_link(h + ww + 1LL, t, 1e18);
        }
        if (c == 'o') {
            mf.add_link(hh + 1LL, h + ww + 1LL, 1);
            mf.add_link(h + ww + 1LL, hh + 1LL, 1);
        }
    }

    ll ans = mf.solve();
    if (ans >= 1e17) cout << -1 << endl;
    else cout << ans << endl;
}

///////////////////////////////////////////////////////////////////////////////


Measured memory_bytes: 4360