Fire!

const int MAXN = 1100;

struct Node
{
    int x, y, foot;
    Node (int x = 0, int y = 0, int foot = 0) : x(x), y(y), foot(foot){}
} people;
char m[MAXN][MAXN];
int step[MAXN][MAXN];
queue<Node> q;
int kase, a, b;

int dx[] = {0, 0, -1, 1};
int dy[] = {-1, 1, 0, 0};

inline void init()
{
    while (!q.empty()) q.pop();
}

void bfs_fire()
{
    Node t;
    while (!q.empty())
    {
        t = q.front();
        q.pop();
        REP(i, 4)
        {
            int tx = t.x + dx[i];
            int ty = t.y + dy[i];
            if (m[tx][ty] == ‘.‘ && step[tx][ty] == INF)
            {
                step[tx][ty] = t.foot + 1;
                q.push(Node(tx, ty, t.foot + 1));
            }
        }
    }
}

bool bfs_people(Node& ans)
{
    while (!q.empty())
    {
        ans = q.front();
        q.pop();
        if (ans.x == 1 || ans.x == a || ans.y == 1 || ans.y == b)
            return true;
        REP(i, 4)
        {
            int tx = ans.x + dx[i];
            int ty = ans.y + dy[i];
            if (m[tx][ty] == ‘.‘ && ans.foot + 1 < step[tx][ty])
            {
                m[tx][ty] = ‘J‘;
                q.push(Node(tx, ty, ans.foot + 1));
            }
        }
    }
    return false;
}

int main()
{
//    freopen("in.txt", "r", stdin);
    RI(kase);
    REP(kk, kase)
    {
        CLR(step, INF);
        CLR(m, ‘#‘);
        init();

        RII(a, b);
        FE(i, 1, a) FE(j, 1, b)
        {
            cin >> m[i][j];
            if (m[i][j] == ‘J‘)
            {
                people.x = i, people.y = j;
                people.foot = 0;
                m[i][j] = ‘.‘;
            }
            else if (m[i][j] == ‘F‘)
            {
                step[i][j] = 0;
                q.push(Node(i, j, 0));
                m[i][j] = ‘.‘;
            }
        }
        bfs_fire();

        init();
        q.push(people);
        m[people.x][people.y] = ‘J‘;
        if (bfs_people(people))
            cout << people.foot + 1 << endl;
        else
            cout << "IMPOSSIBLE" << endl;
    }
    return 0;
}