问题描述：
The Fibonacci sequence is defined by the recurrence relation:
Fn = Fn1 + Fn
Hence the first 12 terms will be:
F1 = 1
F2 = 1
F3 = 2
F4 = 3
F5 = 5
F6 = 8
F7 = 13
F8 = 21
F9 = 34
F10 = 55
F11 = 89
F12 = 144
The 12th term, F12, is the first term to contain three digits.
What is the first term in the Fibonacci sequence to contain 1000 digits?
翻译：
Fibonacci数列的定义如下：
Fn = Fn-1 + Fn-2，且F1 = 1, F2 = 1。
于是前12个Fibonacci数就是：
第十二项F12，是第一个达到三位数的Fibonacci数。
第一个达到1000位的Fibonacci数又是多少呢？
解答：
def isok(a):
count=0
while a>0:
a/=10
count+=1
if count==1000:
return True
return False
a,b,c=1,1,0
count=2
while True:
c=a+b
count+=1
if isok(c):
break
a=b
b=c
print count
projecteuler---->problem=25----1000-digit Fibonacci number,布布扣,bubuko.com
projecteuler---->problem=25----1000-digit Fibonacci number
原文：http://blog.csdn.net/q745401990/article/details/29594073