#!/usr/bin/env python3
n, c = [int(x) for x in input().split()]
dyn = [[0]*n for _ in range(n)] #worst case cost of interval [a,b]
for i in range(n):
    dyn[i][i] = i+1   
for j in range(1, n):
    for i in range(n-j):
        dyn[i][i+j] = min([max(dyn[i][k-1]+k+1, dyn[k+1][i+j]+c) for k in range(i+1, i+j)]+[max(i+1, dyn[i+1][i+j]+c), dyn[i][i+j-1]+i+j+1])
print(dyn[0][n-1])