#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<usize>();
    let (h, w) = (v[0], v[1]);
    let mut grid = vec![vec![]; h];
    for y in 0..h {
        grid[y] = read::<String>().chars().collect::<Vec<_>>();
    }
    let mut start_x = 0usize;
    let mut start_y = 0usize;
    let mut goal_x = 0usize;
    let mut goal_y = 0usize;

    for y in 0..h {
        for x in 0..w {
            if grid[y][x] == 'S' {
                start_y = y;
                start_x = x;
            } else if grid[y][x] == 'T' {
                goal_y = y;
                goal_x = x;
            }
        }
    }
    // [0 ~ w - 1]. [w ~ w + h - 1] [h + w]: start, [h + w + 1]]: goal
    let mut solver = Solver::new(h + w + 2);
    let mut inf = 1000_000_000;
    // to _start
    solver.add_edge_both(start_x, h + w, inf);
    solver.add_edge_both(w + start_y, h + w, inf);

    // to_goal
    solver.add_edge_both(goal_x, h + w + 1, inf);
    solver.add_edge_both(w + goal_y, h + w + 1, inf);

    for y in 0..h {
        for x in 0..w {
            if grid[y][x] == 'o' {
                solver.add_edge_both(x, w + y, 1);
            }
        }
    }

    let ans = solver.max_flow(h + w, h + w + 1);
    if ans >= inf {
        println!("-1");
        return;
    }
    println!("{:?}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

#[derive(Clone, Copy)]
struct Edge {
    to: usize,
    cap: i64,
    rev: usize,
}

#[derive(Clone)]
struct Solver {
    edges: Vec<Vec<Edge>>,
    used: Vec<bool>,
}

impl Solver {
    fn new(v: usize) -> Solver {
        Solver {
            edges: vec![Vec::new(); v],
            used: vec![false; v],
        }
    }

    fn add_edge_both(&mut self, from: usize, to: usize, cap: i64) {
        self.add_edge(from, to, cap);
        self.add_edge(to, from, cap);
    }

    fn add_edge(&mut self, from: usize, to: usize, cap: i64) {
        let rev = self.edges[to].len();
        self.edges[from].push(Edge {
            to: to,
            cap: cap,
            rev: rev,
        });
        let rev = self.edges[from].len() - 1;
        self.edges[to].push(Edge {
            to: from,
            cap: 0,
            rev: rev,
        });
    }

    fn dfs(&mut self, v: usize, t: usize, f: i64) -> i64 {
        if v == t {
            return f;
        }
        self.used[v] = true;
        for i in 0..self.edges[v].len() {
            let edge = self.edges[v][i];
            if !self.used[edge.to] && edge.cap > 0 {
                let d = self.dfs(edge.to, t, std::cmp::min(f, edge.cap));
                if d > 0 {
                    self.edges[v][i].cap -= d;
                    self.edges[edge.to][edge.rev].cap += d;
                    return d;
                }
            }
        }
        0
    }

    fn max_flow(&mut self, s: usize, t: usize) -> i64 {
        let mut flow = 0;
        loop {
            self.used = vec![false; self.edges.len()];
            let f = self.dfs(s, t, std::i64::MAX);
            if f == 0 {
                return flow;
            }
            flow += f;
        }
    }
}


Measured memory_bytes: 4352