Problem:
Score : 100 points

Problem Statement

We have A apples and P pieces of apple.

We can cut an apple into three pieces of apple, and make one apple pie by simmering two pieces of apple in a pan.

Find the maximum number of apple pies we can make with what we have now.

Constraints

All values in input are integers.

0 \leq A, P \leq 100

Input

Input is given from Standard Input in the following format:

A P

Output

Print the maximum number of apple pies we can make with what we have.

Sample Input 1

1 3

Sample Output 1

3

We can first make one apple pie by simmering two of the three pieces of apple. Then, we can make two more by simmering the remaining piece and three more pieces obtained by cutting the whole apple.

Sample Input 2

0 1

Sample Output 2

0

We cannot make an apple pie in this case, unfortunately.

Sample Input 3

32 21

Sample Output 3

58

Solution in Rust (1.15.1) (judge verdict: Accepted)



fn main() {
    let v: Vec<u32> = read_vec();
    let (a, b) = (v[0], v[1]);

    println!("{}", (a * 3 + b) / 2);
}





//**********************************************************************************************************************************************//

// 標準入力から一行を読み取り、指定の型に変換する関数
pub fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

// 標準入力から一行を読み取り、空白文字で分割し、各要素を指定の型に変換する関数
pub fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

// 標準入力からn行を読み取り、各行を空白文字で分割し、各要素を指定の型に変換する関数
pub fn read_vec2<T: std::str::FromStr>(n: u64) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

// 10進数での各桁の和
pub fn sum_dights(x: isize) -> isize {
    if x % 10 == 0 {
        return 0
    }
    let m = x % 10;
    m + sum_dights((x - m) / 10)
}