import sys
input = sys.stdin.readline

N,S=map(int,input().split())

SET=set(range(1,N+1))
SUM=N*(N+1)//2
MAX=N

while SUM>S:
    if SUM-S>MAX:
        SET.remove(MAX)
        SUM-=MAX
        MAX-=1
    else:
        x=SUM-S
        SET.remove(x)
        SUM-=x
        
print(len(SET))
print(*sorted(SET))