P8752 [Lanqiao Cup 2021 NOI Qualifier B2] Special Year

This year is 2021. The number 2021 is very special: its thousands digit equals its tens digit, and its ones digit is greater than its hundreds digit by $1$. We call a year that satisfies these conditions a special year. Given $5$ years, please calculate how many of them are special years.

Input consists of $5$ lines. Each line contains a $4$-digit decimal number (ranging from $1000$ to $9999$), representing a year.

Output an integer, representing how many of the $5$ input years are special years.

**Sample Explanation.** 2021 and 9899 are special years. The others are not special years. Lanqiao Cup 2021, second round provincial contest, Group B, Problem F. Translated by ChatGPT 5