import math

fibo_1 = 1
fibo_2 = 1

index_1000digit = 0
index_10000digit = 0

index = 3

while(1):
    
    fibo_n = fibo_1 + fibo_2
    power10 = int(math.log10(fibo_n))

    if(power10 == 999 and index_1000digit == 0):
        index_1000digit = index

    elif(power10 == 9999 and index_10000digit == 0):
        index_10000digit = index
        break;

    fibo_1 = fibo_2
    fibo_2 = fibo_n
    index = index + 1

print("Index for 1st Fibonacci number with 1000 digits is:", index_1000digit)
print("Index for 1st Fibonacci number with 10000 digits is:", index_10000digit)

# OUTPUT:

# Index for 1st Fibonacci number with 1000 digits is: 4782
# Index for 1st Fibonacci number with 10000 digits is: 47847