#python program with test cases to find the index of 1000 digits fibonacci number
import unittest
def fib_index(n):
    if type(n)!=int:
        return 'Type error'
    if n<1 :
        return None
    count=2
    length=1
    a,b=1,1
    while length!=n:
        c=a+b
        a=b
        b=c
        count+=1
        length=len(str(b))
    return count
print(fib_index(1000))

class test_cases(unittest.TestCase):
    def test_fib_index(self):
        self.assertEqual(fib_index(-10),None)
        self.assertEqual(fib_index('456'), 'Type error')
        self.assertEqual(fib_index(3),12)

if __name__ == "__main__":
    unittest.main()