1 2 3 4 1 2 4 3 1 3 2 4 1 3 4 2 1 4 2 3 1 4 3 2 2 1 3 4 2 1 4 3
for (k=n-1; k>=1; k--) while (m>=k!) { m-=k!; 按照上述规则变化; }