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8 years ago
# The Fibonacci sequence is defined by the recurrence relation:
#
# Fn = Fn1 + Fn2, where F1 = 1 and F2 = 1.
#
# The 12th term, F12, is the first term to contain three digits.
#
# What is the index of the first term in the Fibonacci sequence to contain 1000 digits?
n_minus_1 = 1
n_minus_2 = 1
value = 0
index = 3
while True:
value = n_minus_1 + n_minus_2
if len(str(value)) == 1000:
print(index)
break
n_minus_2 = n_minus_1
n_minus_1 = value
index += 1