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

using vi = vector<int>; using vvi = vector<vi>; using vvvi = vector<vvi>;
using ll = long long int;
using vll = vector<ll>; using vvll = vector<vll>; using vvvll = vector<vvll>;
using vd = vector<double>; using vvd = vector<vd>; using vvvd = vector<vvd>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using cdouble = complex<double>;

const double eps = 1e-7;
const double INFD = numeric_limits<double>::infinity();
#define Loop(i, n) for(int i = 0; i < int(n); i++)
#define Loopll(i, n) for(ll i = 0; i < ll(n); i++)
#define Loop1(i, n) for(int i = 1; i <= int(n); i++)
#define Loopll1(i, n) for(ll i = 1; i <= ll(n); i++)
#define Loopr(i, n) for(int i = int(n) - 1; i >= 0; i--)
#define Looprll(i, n) for(ll i = ll(n) - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = int(n); i >= 1; i--)
#define Looprll1(i, n) for(ll i = ll(n); i >= 1; i--)
#define Foreach(buf, container) for(auto buf : container)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= (h) ? (h) - 1 : (sum)), j = (sum) - i; i >= 0 && j < (w); i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= (w) ? (w) - 1 : (sum)), i = (sum) - j; j >= 0 && i < (h); j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(ex_i, vector.size()) { cout << vector[ex_i] << " "; } cout << endl;
#define printmx(matrix) Loop(ex_i, matrix.size()) { Loop(ex_j, matrix[ex_i].size()) { cout << matrix[ex_i][ex_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
#define Comp(type_t) bool operator<(const type_t &another) const
#define fst first
#define snd second
#define INF INFINITY
bool feq(double x, double y) { return abs(x - y) <= eps; }
bool fge(double x, double y) { return x >= y - eps; }
double fsqrt(double x) { return feq(x, 0) ? 0 : sqrt(x); }
bool inrange(ll x, ll t) { return x >= 0 && x < t; }
bool inrange(vll xs, ll t) { Foreach(x, xs) if (!(x >= 0 && x < t)) return false; return true; }
int ceillog2(ll x) { int ret = 0;	x--; while (x > 0) { ret++; x >>= 1; } return ret; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (m * m <= x ? 0 : -1); }
ll ceilsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }
ll lcm(ll m, ll n) { return m * n / gcd(m, n); }

/*******************************************************/

class Maxflow {
private:
	struct edge_t {
		int cap;
	};
	int n, source, sink;
	int result;
	vector<bool> done;
	vector<unordered_map<int, edge_t>> lst;
	int dfs(int a, int t) {
		if (a == t) return 1;
		done[a] = true;
		Loopitr(itr, lst[a]) {
			int b = itr->fst;
			int cap = itr->snd.cap;
			if (!done[b] && cap > 0) {
				if (dfs(b, t)) {
					lst[a][b].cap--;
					lst[b][a].cap++;
					return 1;
				}
			}
		}
		return 0;
	}
	int run_flow(int s, int t, int f) {
		int ret = 0;
		Loop(i, f) {
			done = vector<bool>(n, false);
			if (dfs(s, t)) ret++;
			else break;
		}
		return ret;
	}
public:
	Maxflow(const vvi &lst, const vvi &cap, int s, int t) {
		n = lst.size();
		this->lst.resize(n);
		Loop(i, n) {
			Loop(j, lst[i].size()) {
				this->lst[i][lst[i][j]].cap += cap[i][j];
				this->lst[lst[i][j]][i].cap += 0;
			}
		}
		source = s;
		sink = t;
		result = 0;
		update();
	}
	void add_cap(int s, int t, int dcap, bool update_flag = true) {
		lst[s][t].cap += dcap;
		// program not be ensured when cap. becomes negative
		if (lst[s][t].cap < 0) {
			int df = -lst[s][t].cap;
			run_flow(s, source, df);
			run_flow(sink, t, df);
			lst[s][t].cap += df;
			lst[t][s].cap -= df;
			result -= df;
		}
		if (update_flag) update();
	}
	void update() {
		result += run_flow(source, sink, INT_MAX);
	}
	int get_maxflow() {
		return result;
	}
};

void failed() {
	cout << -1 << endl;
	exit(0);
}

int main() {
	int h, w;
	cin >> h >> w;
	vector<string> a(h);
	Loop(i, h) {
		cin >> a[i];
	}
	int ofst0 = 0;
	int ofst1 = 1;
	int ofst2 = 1 + h;
	int ofst3 = 1 + h + w;
	int n = 1 + h + w + 1;
	vvi lst(n), cap(n);
	int si, sj, ti, tj;
	Loop(i, h) {
		Loop(j, w) {
			if (a[i][j] == 'S') {
				lst[0].push_back(ofst1 + i);
				cap[0].push_back(1e6);
				lst[0].push_back(ofst2 + j);
				cap[0].push_back(1e6);
				si = i;
				sj = j;
			}
			else if (a[i][j] == 'T') {
				lst[ofst1 + i].push_back(n - 1);
				cap[ofst1 + i].push_back(1e6);
				lst[ofst2 + j].push_back(n - 1);
				cap[ofst2 + j].push_back(1e6);
				ti = i;
				tj = j;
			}
			else if (a[i][j] == 'o') {
				lst[ofst1 + i].push_back(ofst2 + j);
				cap[ofst1 + i].push_back(1);
				lst[ofst2 + j].push_back(ofst1 + i);
				cap[ofst2 + j].push_back(1);
			}
		}
	}
	if (si == ti || sj == tj) failed();
	Maxflow *mf = new Maxflow(lst, cap, 0, n - 1);
	cout << mf->get_maxflow() << endl;
}

Measured memory_bytes: 1408