def most_frequent_word(text):
    words = text.split()
    freq = {}
    for w in words:
        freq[w] = freq.get(w, 0) + 1
    return max(freq, key=freq.get)

def most_frequent_word(text):
    import re
    words = re.findall(r'\w+', text.lower())
    freq = {}
    for w in words:
        freq[w] = freq.get(w, 0) + 1
    return max(freq, key=freq.get)   # doesn’t handle tie-breaking

def most_frequent_word(text):
    import re
    words = re.findall(r'\w+', text.lower())
    freq = {}
    for w in words:
        freq[w] = freq.get(w, 0) + 1
    max_freq = max(freq.values())
    candidates = [w for w, c in freq.items() if c == max_freq]
    return min(candidates)   # lexicographically smallest on tie

def rotate(matrix):
    n = len(matrix)
    rotated = [[0]*n for _ in range(n)]
    for i in range(n):
        for j in range(n):
            rotated[j][n-i-1] = matrix[i][j]
    return rotated

def rotate(matrix):
    n = len(matrix)
    for i in range(n):
        for j in range(n):
            matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

def rotate(matrix):
    n = len(matrix)
    # Step 1: Transpose
    for i in range(n):
        for j in range(i, n):
            matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
    # Step 2: Reverse each row
    for row in matrix:
        row.reverse()