#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;

#define REP(i,n) for(long long i = 0; i < (n); i++)
#define FOR(i, m, n) for(long long i = (m);i < (n); ++i)
#define ALL(obj) (obj).begin(),(obj).end()
#define SPEED cin.tie(0);ios::sync_with_stdio(false);

template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;

const ll MOD = (ll)1e9 + 7;
const ll MOD2 = 998244353;
const ll HIGHINF = (ll)1e18;
const ll LOWINF = (ll)1e15;
const long double PI = 3.1415926535897932384626433;

template<typename T> vector<T> make_v(size_t N,T init){return vector<T>(N,init);}
template<typename... T> auto make_v(size_t N,T... t){return vector<decltype(make_v(t...))>(N,make_v(t...));}
template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;}
template <template <class tmp>  class T, class U> ostream &operator<<(ostream &o, const T<U> &obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr)o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
void print(void) {cout << endl;}
template <class Head> void print(Head&& head) {cout << head;print();}
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);}
template <class T> void chmax(T& a, const T b){a=max<T>(a,b);}
template <class T> void chmin(T& a, const T b){a=min<T>(a,b);}
void YN(bool flg) {cout << ((flg) ? "YES" : "NO") << endl;}
void Yn(bool flg) {cout << ((flg) ? "Yes" : "No") << endl;}
void yn(bool flg) {cout << ((flg) ? "yes" : "no") << endl;}


template <class T> class Dinic {
public:
	struct info {
		int to, rev;
		T cap;
	};
	T ini, inf;
	vector<vector<info>> edge;
	vector<int> level, iter;

	Dinic(int N, T ini, T inf) : edge(N), level(N), iter(N), ini(ini), inf(inf) {
		// do nothing
	}

	void make_edge(int from, int to, T cap) {
		edge[from].push_back({ to, (int)edge[to].size(), cap });
		edge[to].push_back({ from, (int)edge[from].size() - 1, ini });
	}

	void bfs(int start) {
		for (int i = 0; i < level.size(); ++i) level[i] = -1;
		queue<int> q;
		level[start] = 0;
		q.push(start);
		while (q.size()) {
			int from = q.front();
			q.pop();
			for (auto& e : edge[from]) {
				if (e.cap > 0 && level[e.to] < 0) {
					level[e.to] = level[from] + 1;
					q.push(e.to);
				}
			}
		}
	}

	T dfs(int from, int goal, T flow) {
		if (from == goal) return flow;
		for (int& i = iter[from]; i < edge[from].size(); ++i) {
			auto& e = edge[from][i];
			if (e.cap <= 0 || level[from] >= level[e.to]) continue;
			T dflow = dfs(e.to, goal, min(flow, e.cap));
			if (dflow <= 0) continue;
			e.cap -= dflow;
			edge[e.to][e.rev].cap += dflow;
			return dflow;
		}
		return ini;
	}

	T maxflow(int start, int goal) {
		T maxflow = ini;
		while (1) {
			bfs(start);
			if (level[goal] < 0) return maxflow;
			for (int i = 0; i < iter.size(); ++i) iter[i] = 0;
			T flow;
			while ((flow = dfs(start, goal, inf))>0) maxflow += flow;
		}
	}
};

int main() {
	int H,W; cin >> H >> W;
	Dinic<ll> d(2*H*W,0,LOWINF);
	V<string> S(H);
	int s,t;
	for(int i = 0; i < H; ++i) cin >> S[i];
	for(int i = 0; i < H; ++i){
		for(int j = 0; j < W; ++j){
			int n = i*W+j;
			d.make_edge(n,n+H*W,1);

			if(S[i][j]=='S') {
				s = n;
				S[i][j] = 'o';
			}
			if(S[i][j]=='T') {
				t = n;
				S[i][j] = 'o';
			}

			for(int k = 0; k < H; ++k){
				int m = k*W+j;
				if(S[i][j]!='o' || S[k][j]!='o'|| m == n) continue;
				d.make_edge(n+H*W,m,1);
				d.make_edge(m+H*W,n,1);
			}
			for(int k = 0; k < W; ++k){
				int m = i*W+k;
				if(S[i][j]!='o' || S[i][k]!='o'|| m == n) continue;
				d.make_edge(n+H*W,m,1);
				d.make_edge(m+H*W,n,1);
			}
		}
	}
	corner(s%W==t%W || s/W==t/W, -1);
	cout << d.maxflow(s+H*W,t) << endl;

	return 0;
}


Measured memory_bytes: 165248