# Check if each start cell can reach each finish cell
drivable_pairs = []
for start, start_cell in start_cells.items():
    for finish, finish_cell in finish_cells.items():
        # Use dynamic programming to calculate the probability of reaching finish cell
        # starting from start cell
        dp = [[{} for _ in range(C)] for _ in range(R)]
        def dfs(row, col):
            if not isValidCell(row, col, R, C):
                return {}
            if isWall(grid, row, col):
                return {}
            if isHazard(grid, row, col):
                return {(row, col): 0.0}
            if (row, col) in dp[row][col]:
                return dp[row][col][(row, col)]
            neighbors = getNeighbors(row, col, R, C)
            probs = {}
            for r, c in neighbors:
                if (row, col) == (start_cell[0], start_cell[1]):
                    if (r, c) == finish_cell:
                        probs[(r, c)] = 1.0
                        continue
                    elif isHazard(grid, r, c):
                        probs[(r, c)] = 0.0
                        continue
                sub_probs = dfs(r, c)
                for sub_cell, sub_prob in sub_probs.items():
                    if (row, col) == (start_cell[0], start_cell[1]):
                        if sub_cell == finish_cell:
                            probs[(r, c)] = sub_prob * 0.5 + 0.5
                        elif isHazard(grid, sub_cell[0], sub_cell[1]):
                            probs[(r, c)] = sub_prob * 0.5
                        else:
                            probs[(r, c)] = sub_prob * 0.5 + dfs(sub_cell[0], sub_cell[1])[(r, c)] * 0.5
                    else:
                        if sub_cell == finish_cell:
                            probs[(r, c)] = sub_prob *