注：n! = 1×2×3×…×n
def f(): s=0 t=1 for i in range(1,6,2): t=t*i s=s+t return s
def f(): s=0 t=0 for i in range(1,6,2): t=t*i s=s+t return s
def f(): s=0 t=1 for i in range(1,6,2): t=t*i if i%2==1: s=s+t return s
def f(): s=0 t=1 for i in range(1,6): t=t*i if i%2==1: s=s+t return s