#include <bits/stdc++.h>
using namespace std;
const int INF = 1LL << 30;
const int MOD = 1000000007;
int gcd(int a, int b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  int a, p;
  cin >> a >> p;
  cout << a * 3 / 2 << endl;
  return 0;
}
