Two zeros in a binary number#9534
In the binary numeral system, consider a number with digits. The first and last digits of this number are both ones. Additionally, between any two ones, there can be no more than two zeros. Your task is to determine how many such numbers exist.
You are given an integer from the standard input. The constraints are: 1 \leq n \leq 50.
Print the number of binary numbers that meet the specified conditions to the standard output.
Example 2