#!/usr/bin/env python3

(n, c), dp = map(int, input().split()), {}
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)])