#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int A, P;
  cin >> A >> P;
  if (A * 3 % 2 == 0) {
    P = A * 3 / 2;
    cout << P << endl;
  } else {
    P = A * 3 / 2 + 1;
    cout << P << endl;
  }
  return 0;
}
