#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
template<typename T1,typename T2> bool chmin(T1 &a,T2 b){if(a<=b)return 0; a=b; return 1;}
template<typename T1,typename T2> bool chmax(T1 &a,T2 b){if(a>=b)return 0; a=b; return 1;}

int h,w;
string s[101];
bool ng(){
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            if(s[i][j]=='S'){
                for(int k=0;k<h;k++){
                    if(s[k][j]=='T') return true;
                }
                for(int k=0;k<w;k++){
                    if(s[i][k] == 'T') return true;
                }
            }
        }
    }
    return false;
}

template< typename flow_t >
struct Dinic {
    const flow_t INF;

    struct edge {
        int to;
        flow_t cap;
        int rev;
        bool isrev;
        int idx;
    };

    vector< vector< edge > > graph;
    vector< int > min_cost, iter;

    Dinic(int V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

    void add_edge(int from, int to, flow_t cap, int idx = -1) {
        graph[from].emplace_back((edge) {to, cap, (int) graph[to].size(), false, idx});
        graph[to].emplace_back((edge) {from, 0, (int) graph[from].size() - 1, true, idx});
    }

    bool bfs(int s, int t) {
        min_cost.assign(graph.size(), -1);
        queue< int > que;
        min_cost[s] = 0;
        que.push(s);
        while(!que.empty() && min_cost[t] == -1) {
            int p = que.front();
            que.pop();
            for(auto &e : graph[p]) {
                if(e.cap > 0 && min_cost[e.to] == -1) {
                    min_cost[e.to] = min_cost[p] + 1;
                    que.push(e.to);
                }
            }
        }
        return min_cost[t] != -1;
    }

    flow_t dfs(int idx, const int t, flow_t flow) {
        if(idx == t) return flow;
        for(int &i = iter[idx]; i < graph[idx].size(); i++) {
            edge &e = graph[idx][i];
            if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
                flow_t d = dfs(e.to, t, min(flow, e.cap));
                if(d > 0) {
                    e.cap -= d;
                    graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

    flow_t max_flow(int s, int t) {
        flow_t flow = 0;
        while(bfs(s, t)) {
            iter.assign(graph.size(), 0);
            flow_t f = 0;
            while((f = dfs(s, t, INF)) > 0) flow += f;
        }
        return flow;
    }

    void output() {
        for(int i = 0; i < graph.size(); i++) {
            for(auto &e : graph[i]) {
                if(e.isrev) continue;
                auto &rev_e = graph[e.to][e.rev];
                cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
            }
        }
    }
};




signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);

    cin>>h>>w;
    for(int i=0;i<h;i++) cin>>s[i];
    if(ng()) {
        cout << -1 << endl;
        return 0;
    }
    // 0->S, T->h*w+1
    Dinic<int> g(h+w+2);
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            if(s[i][j] == 'S'){
                g.add_edge(0,w+i+1,1e9);
                g.add_edge(0,j+1,1e9);
            }
            if(s[i][j] == 'T'){
                g.add_edge(w+i+1,h+w+1,1e9);
                g.add_edge(j+1,h+w+1,1e9);
            }
            if(s[i][j] == 'o'){
                g.add_edge(w+i+1,j+1,1);
                g.add_edge(j+1,w+i+1,1);
            }
        }
    }
    cout << g.max_flow(0,h+w+1) << endl;
}

Measured memory_bytes: 1280