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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);(i)++)
#define all(x) x.begin(),x.end()
struct revran {
  const i64 b, e;
  struct iter {
    i64 i;
    constexpr iter(const i64 i) noexcept: i(i) {}
    void operator++() noexcept { --i; }
    constexpr i64 operator*() const noexcept { return i; }
    constexpr bool operator!=(const iter x) const noexcept { return i != x.i; }
  };
  constexpr revran(const i64 e) noexcept: b(0), e(e) {}
  constexpr revran(const i64 b, const i64 e) noexcept: b(b), e(e) {}
  constexpr iter begin() const noexcept { return iter(e - 1); }
  constexpr iter end() const noexcept { return iter(b - 1); }
};

struct ran {
  const i64 b, e;
  struct iter {
    i64 i;
    constexpr iter(const i64 i) noexcept: i(i) {}
    void operator++() noexcept { ++i; }
    constexpr i64 operator*() const noexcept { return i; }
    constexpr bool operator!=(const iter x) const noexcept { return i != x.i; }
  };
  constexpr ran(const i64 e) noexcept: b(0), e(e) {}
  constexpr ran(const i64 b, const i64 e) noexcept: b(b), e(e) {}
  constexpr iter begin() const noexcept { return iter(b); }
  constexpr iter end() const noexcept { return iter(e); }
  constexpr revran rev() const noexcept { return revran(b, e); }
};

constexpr ran rin(const i64 e) noexcept { return ran(1, e + 1); }
constexpr ran rin(const i64 b, const i64 e) noexcept { return ran(b, e + 1); }

int main() {
  i64 a,p;
  cin >> a >> p;
  p += a * 3;
  cout << p / 2 << endl;
}