from decimal import Decimal
import math
import numpy as np
def fibgen(n):
    y = math.sqrt(5)
    x = Decimal((1+Decimal(y))**n-(1-Decimal(y))**n)//Decimal(2**n*Decimal(y))
    print(x)
    return x

n=5000
while True:
    if(int(math.log10(fibgen(n))+1) == 1000):
        print(n)
        break
    n += 1