#include <bits/stdc++.h>

using namespace std;

const int vy[] = {1, 0, -1, 0};
const int vx[] = {0, 1, 0, -1};

int N;
string S[3000];
bool v[3000][3000];
int ord[3000][3000], low[3000][3000], k;
int sub[3000][3000];


int rec(int y, int x, int py = -1, int px = -1) {
  v[y][x] = true;
  ord[y][x] = k++;
  low[y][x] = ord[y][x];
  sub[y][x] = S[y][x] == '.';
  int ret = 0, add = 1;
  for(int i = 0; i < 4; i++) {
    int ny = y + vy[i], nx = x + vx[i];
    if(ny < 0 || nx < 0 || ny >= N || nx >= N) continue;
    if(S[ny][nx] == '#') continue;
    if(ny == py && nx == px) continue;
    if(v[ny][nx]) {
      low[y][x] = min(low[y][x], ord[ny][nx]);
    } else {
      ret = max(ret, rec(ny, nx, y, x));
      sub[y][x] += sub[ny][nx];
      low[y][x] = min(low[y][x], low[ny][nx]);
      if(ord[y][x] <= low[ny][nx]) add += sub[ny][nx];
    }
  }
  if(S[y][x] == '.') ret = max(ret, add);
  return ret;
}

int main() {
  cin >> N;
  int all = 0;
  for(int i = 0; i < N; i++) {
    cin >> S[i];
    all += count(begin(S[i]), end(S[i]), '.');
  }
  int res;
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < N; j++) {
      if(S[i][j] == 'T') res = all - rec(i, j);
    }
  }
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < N; j++) {
      if(!v[i][j]) res -= S[i][j] == '.';
    }
  }
  cout << res << endl;
}