ProjectEuler/P025.py at master · mcleu/ProjectEuler · GitHub

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# -*- coding: utf-8 -*-
#===============================================================================
# The Fibonacci sequence is defined by the recurrence relation:
# Fn = Fn1 + Fn2, where F1 = 1 and F2 = 1.
# 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?
#===============================================================================

a=1
b=1
n=2

while 1:
    n += 1
    a,b = a+b, a
    if len(str(a))>=1000:
        break
    # print n, a


print n