#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template<class T>bool chmax(T &a, const T &b) { return (a < b) ? (a = b, 1) : 0;}
template<class T>bool chmin(T &a, const T &b) { return (b < a) ? (a = b, 1) : 0;}

using ll = long long;
using R = long double;
const R EPS = 1e-9L; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R& r) {return (r > EPS) - (r < -EPS);}
inline R sq(R x) {return sqrt(max(x, 0.0L));}

const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};

//Appropriately Changed
using W = ll;
using edge = struct {int to, rev; W cap, flow;};
using G = vector<vector<edge>>;

//Appropriately Changed
void add_edge(G &graph, int from, int to, W cap) {
	graph[from].push_back({to, int(graph[to].size()) , cap , 0});
	graph[to].push_back({from, int(graph[from].size()) - 1, 0 , 0});
}

W dinic(G &graph, int s, int t) {
	const W inf = 1LL << 50;
	const int n = graph.size();
	vector<int> level(n), iter(n);

	auto bfs = [&](int s, int t) {
		fill(begin(level), end(level), -1);
		queue<int> q;
		level[s] = 0, q.push(s);

		while (!q.empty()) {
			int v = q.front(); q.pop();
			for (auto &e : graph[v]) {
				if (level[e.to] == - 1 and e.cap > e.flow) {
					level[e.to] = level[v] + 1;
					q.push(e.to);
				}
			}
		}
		return (level[t] !=  -1);
	};

	auto dfs = [&](int v, int t, W f) {
		auto func = [&](int v, int t, W f, auto func)->W{

			if (v == t) return f;
			for (int &i = iter[v]; i < graph[v].size(); i++) {
				edge &e = graph[v][i];

				if (e.cap > e.flow and level[v] < level[e.to]) {

					W d = func(e.to, t, min(f, e.cap - e.flow), func);

					if (d > 0) {
						e.flow += d, graph[e.to][e.rev].flow -= d;
						return d;
					}
				}
			}

			return 0;
		};
		return func(v, t, f, func);
	};

	while (bfs(s, t)) {
		fill(begin(iter), end(iter), 0);
		while (dfs(s, t, inf) != 0 );
	}

	W ret = 0;
	for (auto &e : graph[s]) ret += e.flow;
	return ret;
}

char pond[110][110];

int main(void) {
	int h, w;
	cin >> h >> w;

	rep(i, h)rep(j, w) cin >> pond[i][j];

	const int s =  h + w;
	const int t =  s + 1;
	const int total = t + 1;

	G graph(total);
	const int inf = 1 << 20;

	//cerr << "OK" << endl;
	
	rep(i, h)rep(j, w) {
		if (pond[i][j] == 'S'){
			add_edge(graph,s,i+w,inf);
			add_edge(graph,s,j,inf);
		}
		
		if (pond[i][j] == 'T'){
			add_edge(graph,i+w,t,inf);
			add_edge(graph,j,t,inf);
		}

		if(pond[i][j]=='o'){
			add_edge(graph,i+w,j,1);
			add_edge(graph,j,i+w,1);
		}
		
	}

	//cerr << "OK" << endl;
	

	//cerr << s << " " << t << endl;

	int ans = dinic(graph, s, t);
	if(ans >= inf) ans = -1;
	cout << ans << endl;


	return 0;
}

Measured memory_bytes: 1536