#!/usr/bin/env python3

n, c = map(int, input().split())
dp = [[0] * (n + 1) for _ in range(n + 1)]
for i in range(1, n + 1): dp[i][i] = i
for d in range(1, n + 1):
    for low in range(1, n + 1 - d):
        high = low + d
        dp[low][high] = min(
            max(
                guess + dp[low][guess - 1] if guess > low else 0,
                c + dp[guess + 1][high] if guess < high else guess
            )
            for guess in range(low, high + 1)
        )
print(dp[1][n])