#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (Y)-1;(X) >= (S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
#define out(args...){vector<string> a_r_g_s=s_p_l_i_t(#args, ','); e_r_r(a_r_g_s.begin(), args); }
vector<string> s_p_l_i_t(const string &s, char c){vector<string> v;int d=0,f=0;string t;for(char c:s){if(!d&&c==',')v.pb(t),t="";else t+=c;if(c=='\"'||c=='\'')f^=1;if(!f&&c=='(')++d;if(!f&&c==')')--d;}v.pb(t);return move(v);}
void e_r_r(vector<string>::iterator it) {}
template<typename T, typename... Args> void e_r_r(vector<string>::iterator it, T a, Args... args){ if(*it==" 1"||*it=="1") cerr<<endl; else cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << ", "; e_r_r(++it, args...);}
const ll MOD=1e9+7;
struct Edge{ll to,cap,rev;};
typedef vector<Edge> Edges;
typedef vector<vector<Edge> > Graph;

void add_edge(Graph &g,int from,int to,ll cap){
  g[from].pb((Edge){to,cap,(int)g[to].size()});
  g[to].pb((Edge){from,0,(int)g[from].size()-1});
}
ll INF=1e9;

//max_flow

vector<int> used;

ll dfs(Graph &g,int v,int t,ll f){
  if(v==t) return f;
  used[v]=1;
  ll i,j,k;
  for(i=0;i<g[v].size();i++){
    Edge &e=g[v][i];
    if(e.cap<=0||used[e.to])continue;
    ll d=dfs(g,e.to,t,min(f,e.cap));
    if(d>0){
      e.cap-=d;
      g[e.to][e.rev].cap+=d;
      return d;
    }
  }
  return 0;
}

ll max_flow(Graph &g,int s,int t){
  ll sum=0,f,V=g.size();
  while(1){
    used.resize(V);
    fill(all(used),0);
    sum+=f=dfs(g,s,t,INF);
    if(!f)return sum;
  }
}

int n,m;
int fun(int x,int y,int t=0){
  assert(x<m && y<n && t<2);
  return x+y*m+t*m*n;
}
int fx(int x){assert(x<m); return n*m*2+x;}
int fy(int y){assert(y<n); return n*m*2+m+y;}

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  cin>>n>>m;
  vector<string> a(n);
  rep(i,n) cin>>a[i];
  Graph g(n*m*2+n+m);
  int s=-1,t=-1;
  int sx,sy,tx,ty;
  rep(i,n)rep(j,m)if(a[i][j]!='.'){
    add_edge(g,fun(j,i,0),fun(j,i,1),1);
    add_edge(g,fun(j,i,1),fx(j),INF);
    add_edge(g,fun(j,i,1),fy(i),INF);
    add_edge(g,fx(j),fun(j,i,0),INF);
    add_edge(g,fy(i),fun(j,i,0),INF);
    if(a[i][j]=='S') s=fun(j,i,1), sx =j, sy=i;
    if(a[i][j]=='T') t=fun(j,i,0), tx=j, ty=i;
  }
  assert(s>=0 && t>=0);
  if(sx==tx || sy==ty){
    cout<<-1<<endl;
    return 0;
  }
  ll re=max_flow(g,s,t);
  cout<<(re==INF?-1:re)<<endl;
  return 0;
}


Measured memory_bytes: 4352