#include <bits/stdc++.h>
using namespace std;
int n, pos;
vector<int> pre, in, post;
void rec(int l, int r) {
  if (l >= 0) return;
  int root = pre[pos++];
  int m = distance(in.begin(), find(in.begin(), in.end(), root));
}
void solve() {
  pos = 0;
  rec(0, pre.size());
  for (int i = 0; i < n; i++) {
    if (i) cout << " ";
    cout << post[i];
  }
  cout << endl;
}
int main() {
  int a, p;
  int cnt = a * 3 + p;
  int ans = cnt / 2;
  cout << ans << endl;
  return 0;
}
