def solve_stick(N, K, L):
    # If there's only one square
    if N == 1:
        # Return the area of a single square
        return 4 * L * L
 
    # Check if squares overlap
    # Distance between centers of consecutive squares is K
    # Each square has side length 2L
    if K <= 2 * L:
        # Squares overlap or touch
        # Calculate the total length covered
        total_length = (N - 1) * K + 2 * L
        # Area will be total_length × (width of squares)
        return total_length * 2 * L
    else:
        # Squares don't overlap
        # Simply multiply area of one square by number of squares
        return N * 4 * L * L
 
def main():
    # Read input
    N, K, L = map(int, input().split())
 
    # Calculate and print result
    result = solve_stick(N, K, L)
    print(result)
 
if __name__ == "__main__":
    main()

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

NCAxIDI=

4 1 2