#ifdef LOCAL111
	#define _GLIBCXX_DEBUG
#else
	#define NDEBUG
#endif
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
const int INF = 1e9;
using namespace std;
template<typename T, typename U> ostream& operator<< (ostream& os, const pair<T,U>& p) { cout << '(' << p.first << ' ' << p.second << ')'; return os; }

typedef long long cost_t;

class Edge {
public:
	int to = -1, from = -1, rev = -1;
	cost_t cost = -1, cap = -1;
	
	Edge(){
	}

	Edge(int x,cost_t y){
		to = x;
		cost = y;
	}

	Edge(int x, int y, cost_t z){
		from = x;
		to = y;
		cost = z;
	}

	Edge(int x, int y, int r, cost_t z){
		from = x;
		to = y;
		cost = z;
		rev = r;
	}

	Edge(int x, int y, int r, cost_t co, cost_t ca){
		from = x;
		to = y;
		cost = co;
		cap = ca;
		rev = r;
	}

	bool operator< (const Edge& x) const {
		if(cost != x.cost) return cost < x.cost;
		return to < x.to;
	}

	bool operator> (const Edge& x) const {
		if(cost != x.cost) return cost > x.cost;
		return to > x.to;
	}
};

class Graph {
private:
	typedef vector<Edge> Edges;
	//const long long int INF = (long long)1e18;
	vector<Edges> v; 
	int n;
public:
	Graph(int x){
		n = x;
		v = vector<Edges>(x);
	}

	Graph(){}

	Edges& operator[](int x){
		return v[x];
	}

	const Edges& operator[](int x) const {
		return v[x];
	}

	int size() const {
		return n;
	}

	void add_edge(int from, const Edge &e){
		v[from].push_back(e);
	}

	void add_edge(int from, int to, cost_t cost = -1, cost_t cap = -1, int rev = -1){
		add_edge(from,Edge(from,to,rev,cost,cap));
	}

	void add_fedge(int from, int to, cost_t cap = -1){
		add_edge(from,to,-1,cap,-1);
	}

	void add_uedge(int from, int to, cost_t cost = -1){
		add_edge(from,to,cost);
		add_edge(to,from,cost);
	}
};

template<unsigned int size>
class Index{
public:
	array<int,size> sizes;
	Index(int first, ...){
		va_list args;
		va_start(args, first);
		int arg = first;
		for(int i = 0; i < (int)size; ++i) {
			sizes[i] = arg;
			arg = va_arg(args,int);
		}
	}
	int operator()(int first, ...){
		va_list args;
		va_start(args, first);
		int arg = first;
		int res = 0;
		int d = 1;
		for(int i = 0; i < (int)size; ++i) {
			res += arg*d;
			d *= sizes[i];
			arg = va_arg(args,int);
		}
		return res;
	}
};


#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
	template<typename T> void dpite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
#else
	#define DEBUG(x) true
	template<typename T> void dpite(T a, T b){ return; }
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<int,int> P;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

cost_t ffMaxFlow(const Graph &g_, int s, int t){
	Graph g = g_;
	assert(s != t);
	int n = g.size();
	for(int i = 0; i < n; ++i) {
		for(int j = 0; j < int(g_[i].size()); j++) {
			auto&& e = g[i][j];
			e.rev = g[e.to].size();
			g.add_edge(e.to,i,-1,0,j);
		}
	}

	cost_t flow = 0;
	while(true){
		vector<bool> used(n,false);

		function<cost_t(int,int,cost_t)> dfs = [&](int v, int t, cost_t f) -> cost_t{
			if(v == t) return f;
			used[v] = true;
			for(auto&& e : g[v]) {
				if(!used[e.to] and e.cap > 0){
					cost_t d = dfs(e.to, t, min(f, e.cap));
					if(d > 0){
						e.cap -= d;
						g[e.to][e.rev].cap += d;
						return d;
					}
				}
			}
			return 0;
		};

		cost_t f = dfs(s,t,INF);
		if(f == 0) return flow;
		flow += f;
	}
}

int main()
{
	ios_init();
	int h,w;
	// GraphVizualizer viz;
	while(cin >> h >> w) {
		vector<string> a(h);
		REP(i,h) cin >> a[i];
		Index<3> in(2,h,w);
		Graph g(2*h*w+h+w);
		int s,t;
		REP(i,h) REP(j,w){
			if(a[i][j] == 'S'){
				s = in(0,i,j);
				a[i][j] = 'o';
			}else if(a[i][j] == 'T'){
				t = in(1,i,j);
				a[i][j] = 'o';
			}
		}
		REP(i,h) REP(j,w){
			if(a[i][j] == 'o'){
				g.add_fedge(in(1,i,j),2*h*w+i,INF);
				g.add_fedge(in(1,i,j),2*h*w+h+j,INF);
				g.add_fedge(2*h*w+i,in(0,i,j),INF);
				g.add_fedge(2*h*w+h+j,in(0,i,j),INF);
				if(in(0,i,j) == s or in(1,i,j) == t){
					g.add_fedge(in(0,i,j),in(1,i,j),INF);
				}else{
					g.add_fedge(in(0,i,j),in(1,i,j),1);
				}
			}
		}
		// viz(g,true,false,true);
		int ans = ffMaxFlow(g,s,t);
		cout << (ans==INF ? -1 : ans) << endl;
	}
	return 0;
}


Measured memory_bytes: 7680