from collections import deque

def rotting_oranges(grid):
    rows = len(grid)
    cols = len(grid[0]) if rows else 0
    queue = deque()
    fresh = 0
    for r in range(rows):
        for c in range(cols):
            if grid[r][c] == 2:
                queue.append((r, c, 0))
            elif grid[r][c] == 1:
                fresh += 1
    minutes = 0
    while queue:
        r, c, time = queue.popleft()
        minutes = max(minutes, time)
        for dr, dc in ((1,0),(-1,0),(0,1),(0,-1)):
            nr, nc = r + dr, c + dc
            if 0 <= nr < rows and 0 <= nc < cols and grid[nr][nc] == 1:
                grid[nr][nc] = 2
                fresh -= 1
                queue.append((nr, nc, time + 1))
    return minutes if fresh == 0 else -1