Help me in solving DSAPROB8 problem

help
,
1

My issue

hidden case failure

My code

def dfs(board, word, i, j, k):
    # Write your code here
    if k == len(word):
        return True
    if i < 0 or i >= len(board) or j < 0 or j >= len(board[0]) or board[i][j] != word[k]:
        return False
    tmp = board[i][j]
    board[i][j] = '#' 
    found = (dfs(board, word, i + 1, j, k + 1) or
             dfs(board, word, i - 1, j, k + 1) or
             dfs(board, word, i, j + 1, k + 1) or
             dfs(board, word, i, j - 1, k + 1))
    board[i][j] = tmp
    return found
    
def word_search(board, word):
    for i in range(len(board)):
        for j in range(len(board[0])):
            if dfs(board, word, i, j, 0):
                return True
    return False

if __name__ == "__main__":
    R, C = map(int, input().split())
    board = [input().split() for _ in range(R)]
    word = input()
    print("true" if word_search(board, word) else "false")

Learning course: Design and Analysis of Algorithms
Problem Link: https://www.codechef.com/learn/course/kl-daa/KLDAA2400I/problems/DSAPROB8