#include <bits/stdc++.h>
using namespace std;
struct fastio {
  fastio() {
    ios::sync_with_stdio(false);
    cout << setprecision(10) << fixed;
    cin.tie(0);
  }
};
fastio _fast_io;
int n, p;
int main() {
  int s = n * 3 + p;
  cout << s / 2 << endl;
  return 0;
}
