'''有一分数序列:2/1,3/2,5/3,8/5,13/8,21/13...求出这个数列的前20项之和。'''
a = 0
b = 1
k = 0
e = []
while True:
c = [a, b, a + b]
d = c[0]
c.pop(0)
a = c[0]
b = c[1]
k += 1
e.append(d)
f = e + c
if k != 100:
continue
else:
print(f)
break
num = 0
v = 2
m = 3
o = 0
while True:
mu = f[v]
zi = f[m]
num = num + zi / mu
v += 1
m += 1
o += 1
if o == 20:
print(num)