#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <functional>
using namespace std;

#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define repq(i,a,n) for(int (i)=(a); (i)<=(n); (i)++)
#define repr(i,a,n) for(int (i)=(a); (i)>=(n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a,b) (abs((a) - (b)) < EPS)
#define EQV(a,b) ( EQ((a).X, (b).X) && EQ((a).Y, (b).Y) )
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dx[]={1, -1, 0, 0};
int dy[]={0, 0, 1, -1};
int const MOD = 1000000007;
ll mod_pow(ll x, ll n) {return (!n)?1:(mod_pow((x*x)%MOD,n/2)*((n&1)?x:1))%MOD;}
int madd(int a, int b) {return (a + b) % MOD;}
int msub(int a, int b) {return (a - b + MOD) % MOD;}
int mmul(int a, int b) {return (a * b) % MOD;}
int minv(int a) {return mod_pow(a, MOD-2);}
int mdiv(int a, int b) {return mmul(a, minv(b));}

namespace std {
    bool operator<(const P& a, const P& b) {
        return a.X != b.X ? a.X < b.X : a.Y < b.Y;
    }
}

int H, W;

template <typename T>
struct Edge {
    int to; T cap, cost; int rev;
    Edge(int t, T c, int r) : to(t), cap(c), rev(r) {}
    Edge(int t, T ca, T co, int r) : to(t), cap(ca), cost(co), rev(r) {}
};

template <typename T>
using Graph = vector< vector< Edge<T> > >;

template <typename T>
struct Flow {
    vector< vector< Edge<T> > > G;
    const T MAXC = 1 << 30;
    int n;
    vector<bool> used;
    vector<int> prevv, preve, dist;
    Flow(int _n) : G(_n), n(_n), used(_n, false), 
        prevv(n), preve(n), dist(n, MAXC) {}

    // G[e.to][e.rev] で逆辺を操作できる
    void add_edge(int from, int to, T cap) {
        G[from].push_back(Edge<T>(to, cap, G[to].size()));
        G[to].push_back(Edge<T>(from, 0, G[from].size() - 1));
    }
    void add_edge(int from, int to, T cap, T cost) {
        G[from].push_back(Edge<T>(to, cap, cost, G[to].size()));
        G[to].push_back(Edge<T>(from, 0, -cost, G[from].size() - 1));
    }

    T dfs(int v, int t, T f) {
        if(v == t) return f;
        used[v] = true;
        for(int i=0; i < G[v].size(); i++) {
            Edge<T> &e = G[v][i];
            if(!used[e.to] && e.cap > 0) {
                T 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;
    }

    T max_flow(int s, int t) {
        T flow = 0;
        while(1) {
            fill(used.begin(), used.end(), false);
            T f = dfs(s, t, INF);
            if(f == 0) return flow;
            flow += f;
        }
    }

    T mincost_flow(int s, int t, T f) {
        T res = 0;
        T ma = MAXC;
        while(f > 0) {
            fill(dist.begin(), dist.end(), ma);
            dist[s] = 0;
            bool update = true;
            while(update) {
                update = false;
                for(int v = 0; v < n; v++) {
                    if(dist[v] == ma) continue;
                    for(int i=0; i<G[v].size(); i++) {
                        Edge<T> &e = G[v][i];
                        if(e.cap>0 && dist[e.to] > dist[v] + e.cost) {
                            dist[e.to] = dist[v] + e.cost;
                            prevv[e.to] = v;
                            preve[e.to] = i;
                            update = true;
                        }
                    }
                }
            }

            if(dist[t] == ma) return -1;
            T d = f;
            for(int v = t; v != s; v = prevv[v]) {
                d = min(d, G[prevv[v]][preve[v]].cap);
            }
            f -= d;
            res += d * dist[t];
            for(int v = t; v != s; v = prevv[v]) {
                Edge<T> &e = G[prevv[v]][preve[v]];
                e.cap -= d;
                G[v][e.rev].cap += d;
            }
        }
        return res;
    }
};

pii getindex(int i, int j) {
    // red vertex and blue vertex
    int vl = i+1;
    int vr = j+H+1;
    return pii(vl, vr);
}

signed main() {
    cin >> H >> W;
    int source = 0, sink = H+W+1;
    Flow<int> fl(H+W+2);
    rep(i,0,H) rep(j,0,W) {
        char c; cin >> c;
        pii temp = getindex(i, j);
        if(c == 'S') {
            fl.add_edge(source, temp.fr, INF);
            fl.add_edge(source, temp.sc, INF);
        }
        if(c == 'T') {
            fl.add_edge(temp.fr, sink, INF);
            fl.add_edge(temp.sc, sink, INF);
        }
        if(c == 'o') {
            fl.add_edge(temp.fr, temp.sc, 1);
            fl.add_edge(temp.sc, temp.fr, 1);
        }
    }
    int cut = fl.max_flow(source, sink);
    cout << (cut >= INF ? -1 : cut) << endl;
    return 0;
}

Measured memory_bytes: 1920