#!/usr/bin/env python3


def main():
    n, c = (int(x) for x in input().split())

    def dp(i, j):
        if i == j:
            return i

        if i > j:
            print(f"AAAA {i} {j}")

            exit()

        return min(
            max(
                # Too low (impossible if k = j because there is always a
                # valid value)
                dp(k + 1, j) + c if k < j else -1,
                # Too high
                dp(i, k - 1) + k if k > i else k,
                # Correct guess
                dp(k, k),
            )
            for k in range(i, j + 1)
        )

    print(dp(1, n))


if __name__ == "__main__":
    main()