#include<bits/stdc++.h>
using namespace std;
#pragma region Macros
#define ll long long
#define ld long double
#define FOR(i,l,r) for(int i=(l);i<(r);++i)
#define REP(i,n) FOR(i,0,n)
#define REPS(i,n) FOR(i,1,n+1)
#define RFOR(i,l,r) for(int i=(l);i>=(r);--i)
#define RREP(i,n) RFOR(i,n-1,0)
#define RREPS(i,n) RFOR(i,n,1)
#define pb push_back
#define eb emplace_back
#define SZ(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
template<class T = ll> using V = vector<T>;
template<class T = ll> using VV = V<V<T>>;
using P = pair<ll, ll>;
#define VEC(type, name, size)\
	V<type> name(size);\
	IN(name)
#define VVEC(type, name, h, w)\
	VV<type> name(h, V<type>(w));\
	IN(name)
#define INT(...)\
	int __VA_ARGS__;\
	IN(__VA_ARGS__)
#define LL(...)\
	ll __VA_ARGS__;\
	IN(__VA_ARGS__)
#define STR(...)\
	string __VA_ARGS__;\
	IN(__VA_ARGS__)
#define CHAR(...)\
	char __VA_ARGS__;\
	IN(__VA_ARGS__)
#define DOUBLE(...)\
	DOUBLE __VA_ARGS__;\
	IN(__VA_ARGS__)
#define LD(...)\
	LD __VA_ARGS__;\
	IN(__VA_ARGS__)
template <class T> void scan(T a) { cin >> a; }
void scan(int &a) { cin >> a; }
void scan(long long &a) { cin >> a; }
void scan(char &a) { cin >> a; }
void scan(double &a) { cin >> a; }
void scan(long double &a) { cin >> a; }
void scan(char a[]) { scanf("%s", a); }
void scan(string &a) { cin >> a; }
template <class T> void scan(V<T> &);
template <class T, class L> void scan(pair<T, L> &);
template <class T> void scan(V<T> &a) { for(auto &i : a) scan(i); }
template <class T, class L> void scan(pair<T, L> &p){ scan(p.first); scan(p.second); }
template <class T> void scan(T &a) { cin >> a; }
void IN() {}
template <class Head, class... Tail> void IN(Head &head, Tail &... tail) { scan(head); IN(tail...); }
template <class T> inline void print(T x){ cout << x << '\n';}
template <class T> V<T> press(V<T> &x){ 
	V<T> res = x;
	sort(all(res));
	res.erase(unique(all(res)), res.end());
	REP(i, SZ(x)){
		x[i] = lower_bound(all(res), x[i]) - res.begin();
	}
	return res;
}
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return true; }return false; }
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return true; }return false; }
inline void Yes(bool b = true) {cout << (b ? "Yes" : "No") << '\n';}
inline void YES(bool b = true) {cout << (b ? "YES" : "NO") << '\n';}
inline void err(bool b = true) {if(b) {cout << -1 << '\n'; exit(0);}}
template<class T> inline void fin(bool b = true, T e = 0) {if(b) {cout << e << '\n'; exit(0);}}
template<class T> T divup(T x, T y) {return (x+(y-1))/y;}
template <typename T> T pow(T a, long long n, T e = 1) {T ret = e; while (n) {if (n & 1) ret *= a; a *= a; n >>= 1; } return ret; }
const ll INF = 1e18;
#pragma endregion

template <typename flow_t>
struct Dinic{
private:
	const flow_t INF;
	struct edge{
		int to;
		flow_t cap;
		int rev;
		bool isrev;
		int idx;
	};
	VV<edge> graph;
	V<int> min_cost, iter;

	bool bfs(int s, int t){
		min_cost.assign(SZ(graph), -1);
		queue<int> que;
		min_cost[s] = 0;
		que.push(s);
		while(!que.empty() and min_cost[t] == -1){
			int p = que.front(); que.pop();
			for(auto &e : graph[p]){
				if(e.cap > 0 and min_cost[e.to] == -1){
					min_cost[e.to] = min_cost[p] + 1;
					que.push(e.to);
				}
			}
		}
		return min_cost[t] != -1;
	}

	flow_t dfs(int idx, const int t, flow_t flow){
		if(idx == t) return flow;
		for(int &i = iter[idx]; i < SZ(graph[idx]); i++){
			edge &e = graph[idx][i];
			if(e.cap > 0 and min_cost[idx] < min_cost[e.to]){
				flow_t d = dfs(e.to, t, min(flow, e.cap));
				if(d > 0){
					e.cap -= d;
					graph[e.to][e.rev].cap += d;
					return d;
				}
			}
		}
		return 0;
	}

public:
	Dinic(int v = 0) : INF(numeric_limits<flow_t>::max()), graph(v) {}

	void add_edge(int from, int to, flow_t cap, int idx = -1){
		graph[from].eb(edge{to, cap, SZ(graph[to]), false, idx});
		graph[to].eb(edge{from, 0, SZ(graph[from]) - 1, true, idx});
	}

	flow_t max_flow(int s, int t){
		flow_t flow = 0;
		while(bfs(s, t)){
			iter.assign(SZ(graph), 0);
			flow_t f = 0;
			while((f = dfs(s, t, INF)) > 0) flow += f;
		}
		return flow;
	}

	void resize(int x){ graph.resize(x);}

	int size(){return SZ(graph);}
};

const int inf = 1e9;
int main(){
	INT(h, w);
	Dinic<int> dinic(h + w + 2);
	VVEC(char, a, h, w);
	REP(i, h) REP(j, w){
		if(a[i][j] == 'S'){
			dinic.add_edge(h + w, i, inf);
			dinic.add_edge(h + w, h + j, inf);
		}
		if(a[i][j] == 'T'){
			dinic.add_edge(i, h + w + 1, inf);
			dinic.add_edge(h + j, h + w + 1, inf);
		}
		if(a[i][j] == 'o'){
			dinic.add_edge(i, h + j, 1);
			dinic.add_edge(h + j, i, 1);
		}
	}
	int res = dinic.max_flow(h + w, h + w + 1);
	print(res >= inf ? -1 : res);
}

Measured memory_bytes: 4272