import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayDeque; import java.util.Queue; import java.util.StringTokenizer; public class Main { static StringBuilder sb = new StringBuilder(); static int R, C; static int[][] paper; static int[] dr = { 1, -1, 0, 0 }; static int[] dc = { 0, 0, 1, -1 }; static Queue fire = new ArrayDeque<>(); static Queue m = new ArrayDeque<>(); public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st; st = new StringTokenizer(br.readLine()); R = Integer.parseInt(st.nextToken()); C = Integer.parseInt(st.nextToken()); paper = new int[R][C]; for (int i = 0; i < R; i++) { char[] c = br.readLine().toCharArray(); for (int j = 0; j < C; j++) { int tmp = c[j]; if (tmp == '#') { paper[i][j] = 1000000; } else if (tmp == 'F') { paper[i][j] = -1; fire.add(new Integer[] { i, j }); } else if (tmp == '.') { paper[i][j] = 0; } else if (tmp == 'J') { paper[i][j] = 1; m.add(new Integer[] { i, j }); } } } goFire(); // for (int i = 0; i < R; i++) { // System.out.println(Arrays.toString(paper[i])); // } // for (int i = 0; i < R; i++) { // System.out.println(Arrays.toString(paper[i])); // } int result = goMan(); System.out.println(result == -1 ? "IMPOSSIBLE" : result); } private static int goMan() { while (!m.isEmpty()) { Integer[] tmp = m.poll(); int r = tmp[0]; int c = tmp[1]; int time = paper[r][c]; for (int i = 0; i < 4; i++) { int nr = r + dr[i]; int nc = c + dc[i]; if (!check(nr, nc)) { continue; } if (paper[nr][nc] < -time) { if (endGame(nr, nc)) { return time + 1; } paper[nr][nc] = time + 1; m.add(new Integer[] { nr, nc }); } } } return -1; } private static boolean endGame(int r, int c) { return r == 0 || r == R - 1 || c == 0 || c == C - 1; } private static void goFire() { while (!fire.isEmpty()) { Integer[] tmp = fire.poll(); int r = tmp[0]; int c = tmp[1]; int time = paper[r][c]; for (int i = 0; i < 4; i++) { int nr = r + dr[i]; int nc = c + dc[i]; if (!check(nr, nc)) { continue; } if (paper[nr][nc] == 0) { paper[nr][nc] = time - 1; fire.add(new Integer[] { nr, nc }); } } } } private static boolean check(int nr, int nc) { return nr >= 0 && nc >= 0 && nr < R && nc < C; } }

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