//#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#pragma GCC optimize("unroll-loops")
/*#pragma GCC optimize("section-anchors")
#pragma GCC optimize("profile-values,profile-reorder-functions,tracer")
#pragma GCC optimize("vpt")
#pragma GCC optimize("rename-registers")
#pragma GCC optimize("move-loop-invariants")
#pragma GCC optimize("unswitch-loops")
#pragma GCC optimize("function-sections")
#pragma GCC optimize("data-sections")
#pragma GCC optimize("branch-target-load-optimize")
#pragma GCC optimize("branch-target-load-optimize2")
#pragma GCC optimize("btr-bb-exclusive")*/
//#pragma comment(linker, "/STACK:367077216")
#define _CRT_SECURE_NO_WARNINGS
#include <chrono>
#include <set>
#include <map>
#include <deque>
#include <string>
#include <cstdint>
#include <cmath>
#include <queue>
#include <cassert>
#include <random>
#include <bitset>
#include <iomanip>
#include <numeric>
#include <time.h>//////////////
#include <ctime>
#include <string>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
//#define endl '\n'
#define mp make_pair
#define pbc push_back
#define pob pop_back()
#define empb emplace_back
#define queuel queue<long long>
#define sqr(a) ((a) * (a))
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define pin(p) cin >> p.first >> p.second;
#define uniq(a) sort(all(a));(a).resize(unique(all(a)) - a.begin());
#define rev(v) reverse(v.begin(), v.end());
#define sout(s, c) for (auto i : s) cout << i << c;
#define pout(p) cout << p.first << " " << p.second;
#define er(v, l, r) erase(v.begin() + l, v.begin() + r);
#define vin(v) for (ll i = 0; i < v.size(); ++i) cin >> v[i];
#define vout(v, c) for (int i = 0; i < v.size(); ++i) cout << v[i] << c;
#define pushi(v, a) for (int i = 0; i < a.size(); ++i) v.push_back(a[i]);
#define fastio() ios_base::sync_with_stdio(0); cout.tie(0); cin.tie(0); srand(time(NULL))
#define dab(v) for(auto i:v)cout<<i<<' ';
#define sp system("pause")
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
using namespace std;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++
mt19937 rnd(time(0) + 228 + 'k' + 'e' + 'k' + 'e' + 'r' + 'o' + 'f' + 'e' + 'y');
const ld EPS = 1e-10;
bool checkprime(int x)
{
	for (int i = 2; i * i <= x; ++i) if (x % i == 0) return 0;
	return 1;
}
const ld PI = acos(-1);
const int MOD7 = 1000000007;
const int MOD9 = 1000000009;
int mod = MOD7;
const int inf = 1e9;
const ll INF = 1e18;
const int MAXW = 1e2 + 1;
const int MAXN = MAXW * MAXW * 2 + 300;

char a[MAXW][MAXW];
int h, w;
struct edge
{
	int a, b, cap, flow;
};
vector<int> g[MAXN];
vector<edge> edges;
void addedge(int a, int b, int cap)
{
	g[a].pbc(edges.size());
	edges.pbc({ a,b,cap,0 });
	g[b].pbc(edges.size());
	edges.pbc({ b,a,0, 0 });
}
vector<int> tx(MAXN);
vector<int> d(MAXN);
int s, t;
bool bfs()
{
	d.assign(MAXN, inf);
	queue<int> q;
	q.push(s);
	d[s] = 0;
	while (q.size())
	{
		int v = q.front();
		q.pop();
		for (int i : g[v])
		{
			int to = edges[i].b;
			if (edges[i].cap - edges[i].flow && d[to] > d[v] + 1)
			{
				d[to] = d[v] + 1;
				q.push(to);
			}
		}
	}
	return d[t] < inf;
}
int dfs(int v, int flow)
{
	if (v == t || !flow) return flow;
	for (; tx[v] < g[v].size(); ++tx[v])
	{
		int to = edges[g[v][tx[v]]].b;
		int tflow = edges[g[v][tx[v]]].cap - edges[g[v][tx[v]]].flow;
		tflow = min(tflow, flow);
		if (d[to] == d[v] + 1)
		{
			int x = dfs(to, tflow);
			edges[g[v][tx[v]]].flow += x;
			edges[g[v][tx[v]] ^ 1].flow -= x;
			if (x)
				return x;
		}
	}
	return 0;
}
int dinic()
{
	int ans = 0;
	while (bfs())
	{
		tx.assign(MAXN, 0);
		while (int x = dfs(s, inf)) ans += x;
	}
	return ans;
}
int en(int i, int j)
{
	return i * w + j;
}
signed main()
{
	fastio();
	cin >> h >> w;
	for (int i = 0; i < h; ++i)
	{
		for (int j = 0; j < w; ++j)
		{
			cin >> a[i][j];
			addedge(en(i, j), en(i, j) + h * w, 1);
			if (a[i][j] == 'S') s = en(i, j);
			if (a[i][j] == 'T') t = en(i, j);
		}
	}
	if (s % w == t % w || s / w == t / w)
	{
		cout << -1;
		return 0;
	}
	s += h * w;
	for (int i = 0; i < h; ++i)
	{
		for (int j = 0; j < w; ++j)
		{
			if (a[i][j] == '.' || a[i][j] =='T') continue;
			for (int jcr = 0; jcr < w; ++jcr)
			{
				if (jcr == j) continue;
				if (a[i][jcr] == '.') continue;
				if (a[i][jcr] == 'S') continue;
				addedge(en(i, j) + h * w, en(i, jcr),1);
			}
			for (int ti = 0; ti < h; ++ti)
			{
				if (ti == i || a[ti][j] == '.' || a[ti][j] == 'S') continue;
				addedge(en(i, j) + h * w, en(ti, j), 1);
			}
		}
	}
	cout << dinic();
	sp;
}

Measured memory_bytes: 86256