#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<bitset>
#include<ctime>
#include<deque>
#include<stack>
#include<functional>
#include<sstream>
//#include<cctype>
//#pragma GCC optimize(2)
using namespace std;
#define maxn 2000005
#define inf 0x7fffffff
//#define INF 1e18
#define rdint(x) scanf("%d",&x)
#define rdllt(x) scanf("%lld",&x)
#define rdult(x) scanf("%lu",&x)
#define rdlf(x) scanf("%lf",&x)
#define rdstr(x) scanf("%s",x)
typedef long long  ll;
typedef unsigned long long ull;
typedef unsigned int U;
#define ms(x) memset((x),0,sizeof(x))
const long long int mod = 1e9 + 7;
#define Mod 1000000000
#define sq(x) (x)*(x)
#define eps 1e-4
typedef pair<int, int> pii;
#define pi acos(-1.0)
//const int N = 1005;
#define REP(i,n) for(int i=0;i<(n);i++)
typedef pair<int, int> pii;
inline ll rd() {
	ll x = 0;
	char c = getchar();
	bool f = false;
	while (!isdigit(c)) {
		if (c == '-') f = true;
		c = getchar();
	}
	while (isdigit(c)) {
		x = (x << 1) + (x << 3) + (c ^ 48);
		c = getchar();
	}
	return f ? -x : x;
}

ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a%b);
}
int sqr(int x) { return x * x; }


/*ll ans;
ll exgcd(ll a, ll b, ll &x, ll &y) {
	if (!b) {
		x = 1; y = 0; return a;
	}
	ans = exgcd(b, a%b, x, y);
	ll t = x; x = y; y = t - a / b * y;
	return ans;
}
*/

int n, m;
int st, ed;
struct node {
	int u, v, nxt, w;
}edge[maxn << 1];

int head[maxn], cnt;

void addedge(int u, int v, int w) {
	edge[cnt].u = u; edge[cnt].v = v; edge[cnt].nxt = head[u];
	edge[cnt].w = w; head[u] = cnt++;
}

int rk[maxn];

int bfs() {
	queue<int>q;
	ms(rk);
	rk[st] = 1;
	q.push(st);
	while (!q.empty()) {
		int tmp = q.front(); q.pop();
		for (int i = head[tmp]; i != -1; i = edge[i].nxt) {
			int to = edge[i].v;
			if (rk[to] || edge[i].w <= 0)continue;
			rk[to] = rk[tmp] + 1; q.push(to);
		}
	}
	return rk[ed];
}

int dfs(int u, int flow) {
	if (u == ed)return flow;
	int add = 0;
	for (int i = head[u]; i != -1 && add < flow; i = edge[i].nxt) {
		int v = edge[i].v;
		if (rk[v] != rk[u] + 1 || !edge[i].w)continue;
		int tmpadd = dfs(v, min(edge[i].w, flow - add));
		if (!tmpadd) { rk[v] = -1; continue; }
		edge[i].w -= tmpadd; edge[i ^ 1].w += tmpadd;
		add += tmpadd;
	}
	return add;
}

int ans;
void dinic() {
	while (bfs())ans += dfs(st, inf);
}
int H, W;
char ch[103][103];

int getpos(int x, int y) {
	return (x - 1)*W + y;
}
int main() {
//	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> H >> W; memset(head, -1, sizeof(head));
	for (int i = 1; i <= H; i++)scanf("%s", ch[i] + 1);
	int hx = 0, hy = 0, wx = 0, wy = 0;
	for (int i = 1; i <= H; i++) {
		for (int j = 1; j <= W; j++) {
			if (ch[i][j] == 'S') {
				hx = i; hy = j;
			}
			else if (ch[i][j] == 'T') {
				wx = i; wy = j;
			}
		}
	}
	if (wx == hx || wy == hy) {
		cout << -1 << endl; return 0;
	}
	st = 0; ed = H * W + 1;
	for (int i = 1; i <= H; i++) {
		for (int j = 1; j <= W; j++) {
			if (ch[i][j] == 'S')addedge(st, i, inf), addedge(i, st, 0), addedge(st, j + H, inf), addedge(j + H, st, 0);
			if (ch[i][j] == 'T')addedge(i, ed, inf), addedge(ed, i, 0), addedge(j + H, ed, inf), addedge(ed, j + H, 0);
			if (ch[i][j] != '.')addedge(i, j + H, 1), addedge(j + H, i, 0), addedge(j + H, i, 1), addedge(i, j + H, 0);

		}
	}
	dinic();
	if (ans != inf) {
		cout << ans << endl; return 0;
	}
	else cout << -1 << endl;
	return 0;
}

Measured memory_bytes: 16640