#include<bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define rrep(i,n) for (int i = (n)-1; i >= 0; i--)
#define rep2(i,s,n) for (int i = (s); i < (n); ++i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define pb push_back
#define eb emplace_back
#define vi vector<int>
#define vvi vector<vector<int>>
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vs vector<string>
#define vc vector<char>
#define vb vector<bool>
#define vp vector<P>
using namespace std;
using ll = long long;
using P = pair<int,int>;
using LP = pair<ll,ll>;
template<class T> istream& operator>>(istream& is,vector<T>& v) { for(T& t:v){is>>t;} return is; }
template<class T> ostream& operator<<(ostream& os,const vector<T>& v) { for(T t:v){os<<t<<" ";} os<<"\n"; return os; }
void Yes(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YES(bool b) { cout << (b ? "YES" : "NO") << endl; }
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;}
const int inf = 1001001001;
const ll linf = 1001001001001001001;

class flow {
    struct edge {
        int to,cap,rev;
        edge(int to,int cap,int rev):to(to),cap(cap),rev(rev) {}
    };
    int n;
    vector<vector<edge>> G;
    vi level,iter;

    void bfs(int s) {
        level.assign(n,-1);
        queue<int> q;
        level[s] = 0;
        q.push(s);
        while(!q.empty()) {
            int v = q.front();
            q.pop();
            for(auto& e : G[v]) {
                if(e.cap > 0 && level[e.to] < 0) {
                    level[e.to] = level[v]+1;
                    q.push(e.to);
                }
            }
        }
    }
    int dfs(int v,int t,int f) {
        if(v == t) return f;
        rep2(i,iter[v],G[v].size()) {
            auto &e = G[v][i];
            if(e.cap > 0 && level[v] < level[e.to]) {
                int d = dfs(e.to,t,min(f,e.cap));
                if(d > 0) {
                    e.cap -= d;
                    G[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

public:
    explicit flow(int n):n(n),G(n),level(n),iter(n) {}
    void add_edge(int from,int to,int cap) {
        G[from].eb(to,cap,G[to].size());
        G[to].eb(from,0,G[from].size()-1);
    }
    // O(|E||V|^2) dinic-algorithm
    int max_flow(int s,int t) {
        int fl = 0;
        while(true) {
            bfs(s);
            if(level[t] < 0) return fl;
            iter.assign(n,0);
            int f;
            while((f = dfs(s,t,inf)) > 0) fl += f;
        }
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    int h,w;
    cin >> h >> w;
    flow fl(h+w+2);
    int si,sj,ti,tj;
    rep(i,h) rep(j,w) {
        char a;
        cin >> a;
        if(a == '.') continue;
        if(a == 'S') {
            fl.add_edge(h+w,i,inf);
            fl.add_edge(h+w,h+j,inf);
            si = i,sj = j;
        } else if(a == 'T') {
            fl.add_edge(i,h+w+1,inf);
            fl.add_edge(h+j,h+w+1,inf);
            ti = i,tj = j;
        } else {
            fl.add_edge(i,h+j,1);
            fl.add_edge(h+j,i,1);
        }
    }
    if(si == ti || sj == tj) {
        cout << -1 << endl;
        return 0;
    }
    cout << fl.max_flow(h+w,h+w+1) << endl;
}


Measured memory_bytes: 896